diff --git a/CMakeLists.txt b/CMakeLists.txt
index ae0f8ea29..15ceebe78 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -3,7 +3,9 @@ set(CMAKE_ALLOW_LOOSE_LOOP_CONSTRUCTS ON)
 
 project(zlib C)
 
-set(VERSION "1.3.0.1")
+set(VERSION "1.3.1")
+
+option(ZLIB_BUILD_EXAMPLES "Enable Zlib Examples" ON)
 
 set(INSTALL_BIN_DIR "${CMAKE_INSTALL_PREFIX}/bin" CACHE PATH "Installation directory for executables")
 set(INSTALL_LIB_DIR "${CMAKE_INSTALL_PREFIX}/lib" CACHE PATH "Installation directory for libraries")
@@ -148,7 +150,9 @@ if(MINGW)
 endif(MINGW)
 
 add_library(zlib SHARED ${ZLIB_SRCS} ${ZLIB_DLL_SRCS} ${ZLIB_PUBLIC_HDRS} ${ZLIB_PRIVATE_HDRS})
+target_include_directories(zlib PUBLIC ${CMAKE_CURRENT_BINARY_DIR} ${CMAKE_CURRENT_SOURCE_DIR})
 add_library(zlibstatic STATIC ${ZLIB_SRCS} ${ZLIB_PUBLIC_HDRS} ${ZLIB_PRIVATE_HDRS})
+target_include_directories(zlibstatic PUBLIC ${CMAKE_CURRENT_BINARY_DIR} ${CMAKE_CURRENT_SOURCE_DIR})
 set_target_properties(zlib PROPERTIES DEFINE_SYMBOL ZLIB_DLL)
 set_target_properties(zlib PROPERTIES SOVERSION 1)
 
@@ -166,7 +170,7 @@ endif()
 if(UNIX)
     # On unix-like platforms the library is almost always called libz
    set_target_properties(zlib zlibstatic PROPERTIES OUTPUT_NAME z)
-   if(NOT APPLE)
+   if(NOT APPLE AND NOT(CMAKE_SYSTEM_NAME STREQUAL AIX))
      set_target_properties(zlib PROPERTIES LINK_FLAGS "-Wl,--version-script,\"${CMAKE_CURRENT_SOURCE_DIR}/zlib.map\"")
    endif()
 elseif(BUILD_SHARED_LIBS AND WIN32)
@@ -193,21 +197,22 @@ endif()
 #============================================================================
 # Example binaries
 #============================================================================
-
-add_executable(example test/example.c)
-target_link_libraries(example zlib)
-add_test(example example)
-
-add_executable(minigzip test/minigzip.c)
-target_link_libraries(minigzip zlib)
-
-if(HAVE_OFF64_T)
-    add_executable(example64 test/example.c)
-    target_link_libraries(example64 zlib)
-    set_target_properties(example64 PROPERTIES COMPILE_FLAGS "-D_FILE_OFFSET_BITS=64")
-    add_test(example64 example64)
-
-    add_executable(minigzip64 test/minigzip.c)
-    target_link_libraries(minigzip64 zlib)
-    set_target_properties(minigzip64 PROPERTIES COMPILE_FLAGS "-D_FILE_OFFSET_BITS=64")
+if(ZLIB_BUILD_EXAMPLES)
+    add_executable(example test/example.c)
+    target_link_libraries(example zlib)
+    add_test(example example)
+
+    add_executable(minigzip test/minigzip.c)
+    target_link_libraries(minigzip zlib)
+
+    if(HAVE_OFF64_T)
+        add_executable(example64 test/example.c)
+        target_link_libraries(example64 zlib)
+        set_target_properties(example64 PROPERTIES COMPILE_FLAGS "-D_FILE_OFFSET_BITS=64")
+        add_test(example64 example64)
+
+        add_executable(minigzip64 test/minigzip.c)
+        target_link_libraries(minigzip64 zlib)
+        set_target_properties(minigzip64 PROPERTIES COMPILE_FLAGS "-D_FILE_OFFSET_BITS=64")
+    endif()
 endif()
diff --git a/ChangeLog b/ChangeLog
index dfd652469..b801a1031 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,8 +1,15 @@
 
                 ChangeLog file for zlib
 
-Changes in 1.3.0.1 (xx Aug 2023)
-- 
+Changes in 1.3.1 (22 Jan 2024)
+- Reject overflows of zip header fields in minizip
+- Fix bug in inflateSync() for data held in bit buffer
+- Add LIT_MEM define to use more memory for a small deflate speedup
+- Fix decision on the emission of Zip64 end records in minizip
+- Add bounds checking to ERR_MSG() macro, used by zError()
+- Neutralize zip file traversal attacks in miniunz
+- Fix a bug in ZLIB_DEBUG compiles in check_match()
+- Various portability and appearance improvements
 
 Changes in 1.3 (18 Aug 2023)
 - Remove K&R function definitions and zlib2ansi
diff --git a/FAQ b/FAQ
index 55f1cdc22..92f5d3e29 100644
--- a/FAQ
+++ b/FAQ
@@ -14,8 +14,7 @@ The latest zlib FAQ is at http://zlib.net/zlib_faq.html
  2. Where can I get a Windows DLL version?
 
     The zlib sources can be compiled without change to produce a DLL.  See the
-    file win32/DLL_FAQ.txt in the zlib distribution.  Pointers to the
-    precompiled DLL are found in the zlib web site at http://zlib.net/ .
+    file win32/DLL_FAQ.txt in the zlib distribution.
 
  3. Where can I get a Visual Basic interface to zlib?
 
diff --git a/Makefile.in b/Makefile.in
index b584073b6..cb8b00a9b 100644
--- a/Makefile.in
+++ b/Makefile.in
@@ -1,5 +1,5 @@
 # Makefile for zlib
-# Copyright (C) 1995-2017 Jean-loup Gailly, Mark Adler
+# Copyright (C) 1995-2024 Jean-loup Gailly, Mark Adler
 # For conditions of distribution and use, see copyright notice in zlib.h
 
 # To compile and test, type:
@@ -22,13 +22,13 @@ CFLAGS=-O
 
 SFLAGS=-O
 LDFLAGS=
-TEST_LDFLAGS=$(LDFLAGS) -L. libz.a
+TEST_LIBS=-L. libz.a
 LDSHARED=$(CC)
 CPP=$(CC) -E
 
 STATICLIB=libz.a
 SHAREDLIB=libz.so
-SHAREDLIBV=libz.so.1.3.0.1
+SHAREDLIBV=libz.so.1.3.1
 SHAREDLIBM=libz.so.1
 LIBS=$(STATICLIB) $(SHAREDLIBV)
 
@@ -282,10 +282,10 @@ placebo $(SHAREDLIBV): $(PIC_OBJS) libz.a
 	-@rmdir objs
 
 example$(EXE): example.o $(STATICLIB)
-	$(CC) $(CFLAGS) -o $@ example.o $(TEST_LDFLAGS)
+	$(CC) $(CFLAGS) $(LDFLAGS) -o $@ example.o $(TEST_LIBS)
 
 minigzip$(EXE): minigzip.o $(STATICLIB)
-	$(CC) $(CFLAGS) -o $@ minigzip.o $(TEST_LDFLAGS)
+	$(CC) $(CFLAGS) $(LDFLAGS) -o $@ minigzip.o $(TEST_LIBS)
 
 examplesh$(EXE): example.o $(SHAREDLIBV)
 	$(CC) $(CFLAGS) -o $@ example.o $(LDFLAGS) -L. $(SHAREDLIBV)
@@ -294,10 +294,10 @@ minigzipsh$(EXE): minigzip.o $(SHAREDLIBV)
 	$(CC) $(CFLAGS) -o $@ minigzip.o $(LDFLAGS) -L. $(SHAREDLIBV)
 
 example64$(EXE): example64.o $(STATICLIB)
-	$(CC) $(CFLAGS) -o $@ example64.o $(TEST_LDFLAGS)
+	$(CC) $(CFLAGS) $(LDFLAGS) -o $@ example64.o $(TEST_LIBS)
 
 minigzip64$(EXE): minigzip64.o $(STATICLIB)
-	$(CC) $(CFLAGS) -o $@ minigzip64.o $(TEST_LDFLAGS)
+	$(CC) $(CFLAGS) $(LDFLAGS) -o $@ minigzip64.o $(TEST_LIBS)
 
 install-libs: $(LIBS)
 	-@if [ ! -d $(DESTDIR)$(exec_prefix)  ]; then mkdir -p $(DESTDIR)$(exec_prefix); fi
@@ -360,7 +360,7 @@ zconf: $(SRCDIR)zconf.h.in
 	cp -p $(SRCDIR)zconf.h.in zconf.h
 
 minizip-test: static
-	cd contrib/minizip && { CFLAGS="$(CFLAGS)" $(MAKE) test ; cd ../.. ; }
+	cd contrib/minizip && { CC="$(CC)" CFLAGS="$(CFLAGS)" $(MAKE) test ; cd ../.. ; }
 
 minizip-clean:
 	cd contrib/minizip && { $(MAKE) clean ; cd ../.. ; }
diff --git a/README b/README
index 20f7064a5..c5f917540 100644
--- a/README
+++ b/README
@@ -1,6 +1,6 @@
 ZLIB DATA COMPRESSION LIBRARY
 
-zlib 1.3.0.1 is a general purpose data compression library.  All the code is
+zlib 1.3.1 is a general purpose data compression library.  All the code is
 thread safe.  The data format used by the zlib library is described by RFCs
 (Request for Comments) 1950 to 1952 in the files
 http://tools.ietf.org/html/rfc1950 (zlib format), rfc1951 (deflate format) and
@@ -31,7 +31,7 @@ Mark Nelson <markn@ieee.org> wrote an article about zlib for the Jan.  1997
 issue of Dr.  Dobb's Journal; a copy of the article is available at
 https://marknelson.us/posts/1997/01/01/zlib-engine.html .
 
-The changes made in version 1.3.0.1 are documented in the file ChangeLog.
+The changes made in version 1.3.1 are documented in the file ChangeLog.
 
 Unsupported third party contributions are provided in directory contrib/ .
 
@@ -83,7 +83,7 @@ Acknowledgments:
 
 Copyright notice:
 
- (C) 1995-2023 Jean-loup Gailly and Mark Adler
+ (C) 1995-2024 Jean-loup Gailly and Mark Adler
 
   This software is provided 'as-is', without any express or implied
   warranty.  In no event will the authors be held liable for any damages
diff --git a/build.zig b/build.zig
new file mode 100644
index 000000000..b07483b10
--- /dev/null
+++ b/build.zig
@@ -0,0 +1,63 @@
+const builtin = @import("builtin");
+const std = @import("std");
+const Path = std.Build.LazyPath;
+
+pub fn build(b: *std.Build) void {
+    const optimize = b.standardOptimizeOption(.{});
+    const target = b.standardTargetOptions(.{});
+
+    var lib = b.addStaticLibrary(.{
+        .name = "zlib",
+        .target = target,
+        .optimize = optimize,
+    });
+
+    var source_files = std.ArrayList([]const u8).init(b.allocator);
+    defer source_files.deinit();
+    var flags = std.ArrayList([]const u8).init(b.allocator);
+    defer flags.deinit();
+
+    // const config_header = b.addConfigHeader(
+    //     .{
+    //         .style = .{ .cmake = b.path("zconf.h.cmakein") }
+    //     },
+    //     .{
+    //         .GLOBAL_CLIENT_CONFIG = "KLLtestzlibclientconfig",
+    //     },
+    // );
+    // lib.addConfigHeader(config_header);
+
+    flags.appendSlice(&.{
+        "-Wall",
+        "-Wextra",
+        "-Wpedantic",
+    }) catch unreachable;
+
+    source_files.appendSlice(&.{
+        "adler32.c",
+        "compress.c",
+        "crc32.c",
+        "deflate.c",
+        "gzclose.c",
+        "gzlib.c",
+        "gzread.c",
+        "gzwrite.c",
+        "infback.c",
+        "inffast.c",
+        "inflate.c",
+        "inftrees.c",
+        "trees.c",
+        "uncompr.c",
+        "zutil.c",
+    }) catch unreachable;
+
+    lib.addCSourceFiles(.{
+        .files = source_files.items,
+        .flags = flags.items,
+    });
+
+    lib.linkLibC();
+    lib.installHeader(b.path("zlib.h"), "zlib.h");
+
+    b.installArtifact(lib);
+}
diff --git a/build.zig.zon b/build.zig.zon
new file mode 100644
index 000000000..e80b2141c
--- /dev/null
+++ b/build.zig.zon
@@ -0,0 +1,17 @@
+.{
+    .name = "zlib",
+    // This is a [Semantic Version](https://semver.org/).
+    // In a future version of Zig it will be used for package deduplication.
+    .version = "1.31.1",
+
+    // This field is optional.
+    // This is currently advisory only; Zig does not yet do anything
+    // with this value.
+    //.minimum_zig_version = "0.11.0",
+
+    .paths = .{
+        "LICENSE",
+        "README",
+        "build.zig",
+    },
+}
diff --git a/configure b/configure
index 7aaf5dfa3..c55098afc 100755
--- a/configure
+++ b/configure
@@ -25,7 +25,7 @@ if test $SRCDIR = "."; then
     ZINCOUT="-I."
     SRCDIR=""
 else
-    ZINC='-include zconf.h'
+    ZINC='-I. -include zconf.h'
     ZINCOUT='-I. -I$(SRCDIR)'
     SRCDIR="$SRCDIR/"
 fi
@@ -442,7 +442,7 @@ EOF
 if test $shared -eq 1; then
   echo Checking for shared library support... | tee -a configure.log
   # we must test in two steps (cc then ld), required at least on SunOS 4.x
-  if try $CC -w -c $SFLAGS $test.c &&
+  if try $CC -c $SFLAGS $test.c &&
      try $LDSHARED $SFLAGS -o $test$shared_ext $test.o; then
     echo Building shared library $SHAREDLIBV with $CC. | tee -a configure.log
   elif test -z "$old_cc" -a -z "$old_cflags"; then
diff --git a/contrib/delphi/ZLib.pas b/contrib/delphi/ZLib.pas
index 814ffa670..93fa4c9ed 100644
--- a/contrib/delphi/ZLib.pas
+++ b/contrib/delphi/ZLib.pas
@@ -152,7 +152,7 @@ procedure DecompressToUserBuf(const InBuf: Pointer; InBytes: Integer;
   const OutBuf: Pointer; BufSize: Integer);
 
 const
-  zlib_version = '1.3.0';
+  zlib_version = '1.3.1';
 
 type
   EZlibError = class(Exception);
diff --git a/contrib/dotzlib/DotZLib/ChecksumImpl.cs b/contrib/dotzlib/DotZLib/ChecksumImpl.cs
index c1230bf03..de88dcf11 100644
--- a/contrib/dotzlib/DotZLib/ChecksumImpl.cs
+++ b/contrib/dotzlib/DotZLib/ChecksumImpl.cs
@@ -34,7 +34,7 @@ public ChecksumGeneratorBase()
         }
 
         /// <summary>
-        /// Initializes a new instance of the checksum generator basewith a specified value
+        /// Initializes a new instance of the checksum generator base with a specified value
         /// </summary>
         /// <param name="initialValue">The value to set the current checksum to</param>
         public ChecksumGeneratorBase(uint initialValue)
diff --git a/contrib/dotzlib/DotZLib/UnitTests.cs b/contrib/dotzlib/DotZLib/UnitTests.cs
index c5fce221a..d4f098023 100644
--- a/contrib/dotzlib/DotZLib/UnitTests.cs
+++ b/contrib/dotzlib/DotZLib/UnitTests.cs
@@ -156,7 +156,7 @@ public class InfoTests
         public void Info_Version()
         {
             Info info = new Info();
-            Assert.AreEqual("1.3.0", Info.Version);
+            Assert.AreEqual("1.3.1", Info.Version);
             Assert.AreEqual(32, info.SizeOfUInt);
             Assert.AreEqual(32, info.SizeOfULong);
             Assert.AreEqual(32, info.SizeOfPointer);
diff --git a/contrib/infback9/inftree9.c b/contrib/infback9/inftree9.c
index 23f305010..ac707ed3f 100644
--- a/contrib/infback9/inftree9.c
+++ b/contrib/infback9/inftree9.c
@@ -1,5 +1,5 @@
 /* inftree9.c -- generate Huffman trees for efficient decoding
- * Copyright (C) 1995-2023 Mark Adler
+ * Copyright (C) 1995-2024 Mark Adler
  * For conditions of distribution and use, see copyright notice in zlib.h
  */
 
@@ -9,7 +9,7 @@
 #define MAXBITS 15
 
 const char inflate9_copyright[] =
-   " inflate9 1.3.0.1 Copyright 1995-2023 Mark Adler ";
+   " inflate9 1.3.1 Copyright 1995-2024 Mark Adler ";
 /*
   If you use the zlib library in a product, an acknowledgment is welcome
   in the documentation of your product. If for some reason you cannot
@@ -59,7 +59,7 @@ int inflate_table9(codetype type, unsigned short FAR *lens, unsigned codes,
     static const unsigned short lext[31] = { /* Length codes 257..285 extra */
         128, 128, 128, 128, 128, 128, 128, 128, 129, 129, 129, 129,
         130, 130, 130, 130, 131, 131, 131, 131, 132, 132, 132, 132,
-        133, 133, 133, 133, 144, 70, 200};
+        133, 133, 133, 133, 144, 203, 77};
     static const unsigned short dbase[32] = { /* Distance codes 0..31 base */
         1, 2, 3, 4, 5, 7, 9, 13, 17, 25, 33, 49,
         65, 97, 129, 193, 257, 385, 513, 769, 1025, 1537, 2049, 3073,
diff --git a/contrib/infback9/inftree9.h b/contrib/infback9/inftree9.h
index 2c1252f57..ab2ea28b2 100644
--- a/contrib/infback9/inftree9.h
+++ b/contrib/infback9/inftree9.h
@@ -41,8 +41,8 @@ typedef struct {
    examples/enough.c found in the zlib distribution.  The arguments to that
    program are the number of symbols, the initial root table size, and the
    maximum bit length of a code.  "enough 286 9 15" for literal/length codes
-   returns returns 852, and "enough 32 6 15" for distance codes returns 594.
-   The initial root table size (9 or 6) is found in the fifth argument of the
+   returns 852, and "enough 32 6 15" for distance codes returns 594. The
+   initial root table size (9 or 6) is found in the fifth argument of the
    inflate_table() calls in infback9.c.  If the root table size is changed,
    then these maximum sizes would be need to be recalculated and updated. */
 #define ENOUGH_LENS 852
diff --git a/contrib/iostream3/zfstream.h b/contrib/iostream3/zfstream.h
index 8574479ae..3dabc0f97 100644
--- a/contrib/iostream3/zfstream.h
+++ b/contrib/iostream3/zfstream.h
@@ -413,7 +413,7 @@ template<typename T1, typename T2>
   class gzomanip2
   {
   public:
-    // Allows insertor to peek at internals
+    // Allows inserter to peek at internals
     template <typename Ta, typename Tb>
       friend gzofstream&
       operator<<(gzofstream&,
@@ -452,7 +452,7 @@ template<typename T1, typename T2>
   : func(f), val1(v1), val2(v2)
   { }
 
-// Insertor applies underlying manipulator function to stream
+// Inserter applies underlying manipulator function to stream
 template<typename T1, typename T2>
   inline gzofstream&
   operator<<(gzofstream& s, const gzomanip2<T1,T2>& m)
diff --git a/contrib/minizip/Makefile b/contrib/minizip/Makefile
index aac76e07f..3d927ec14 100644
--- a/contrib/minizip/Makefile
+++ b/contrib/minizip/Makefile
@@ -1,4 +1,4 @@
-CC=cc
+CC?=cc
 CFLAGS := $(CFLAGS) -O -I../..
 
 UNZ_OBJS = miniunz.o unzip.o ioapi.o ../../libz.a
diff --git a/contrib/minizip/configure.ac b/contrib/minizip/configure.ac
index cdfee49cd..15ec91718 100644
--- a/contrib/minizip/configure.ac
+++ b/contrib/minizip/configure.ac
@@ -1,7 +1,7 @@
 #                                               -*- Autoconf -*-
 # Process this file with autoconf to produce a configure script.
 
-AC_INIT([minizip], [1.3.0.1], [bugzilla.redhat.com])
+AC_INIT([minizip], [1.3.1], [bugzilla.redhat.com])
 AC_CONFIG_SRCDIR([minizip.c])
 AM_INIT_AUTOMAKE([foreign])
 LT_INIT
diff --git a/contrib/minizip/ioapi.h b/contrib/minizip/ioapi.h
index c588a18d0..a2d2e6e60 100644
--- a/contrib/minizip/ioapi.h
+++ b/contrib/minizip/ioapi.h
@@ -144,7 +144,7 @@ typedef long     (ZCALLBACK *tell_file_func)      (voidpf opaque, voidpf stream)
 typedef long     (ZCALLBACK *seek_file_func)      (voidpf opaque, voidpf stream, uLong offset, int origin);
 
 
-/* here is the "old" 32 bits structure structure */
+/* here is the "old" 32 bits structure */
 typedef struct zlib_filefunc_def_s
 {
     open_file_func      zopen_file;
diff --git a/contrib/minizip/miniunz.c b/contrib/minizip/miniunz.c
index a12aec8be..d627c4226 100644
--- a/contrib/minizip/miniunz.c
+++ b/contrib/minizip/miniunz.c
@@ -79,7 +79,7 @@
 
 /* change_file_date : change the date/time of a file
     filename : the filename of the file where date/time must be modified
-    dosdate : the new date at the MSDos format (4 bytes)
+    dosdate : the new date at the MSDOS format (4 bytes)
     tmu_date : the SAME new date at the tm_unz format */
 static void change_file_date(const char *filename, uLong dosdate, tm_unz tmu_date) {
 #ifdef _WIN32
@@ -186,7 +186,7 @@ static int makedir(const char *newdir) {
 }
 
 static void do_banner(void) {
-    printf("MiniUnz 1.01b, demo of zLib + Unz package written by Gilles Vollant\n");
+    printf("MiniUnz 1.1, demo of zLib + Unz package written by Gilles Vollant\n");
     printf("more info at http://www.winimage.com/zLibDll/unzip.html\n\n");
 }
 
@@ -356,6 +356,20 @@ static int do_extract_currentfile(unzFile uf, const int* popt_extract_without_pa
         else
             write_filename = filename_withoutpath;
 
+        if (write_filename[0]!='\0')
+        {
+            const char* relative_check = write_filename;
+            while (relative_check[1]!='\0')
+            {
+                if (relative_check[0]=='.' && relative_check[1]=='.')
+                    write_filename = relative_check;
+                relative_check++;
+            }
+        }
+
+        while (write_filename[0]=='/' || write_filename[0]=='.')
+            write_filename++;
+
         err = unzOpenCurrentFilePassword(uf,password);
         if (err!=UNZ_OK)
         {
diff --git a/contrib/minizip/unzip.c b/contrib/minizip/unzip.c
index ed763f89f..ea05b7d62 100644
--- a/contrib/minizip/unzip.c
+++ b/contrib/minizip/unzip.c
@@ -117,7 +117,7 @@
 const char unz_copyright[] =
    " unzip 1.01 Copyright 1998-2004 Gilles Vollant - http://www.winimage.com/zLibDll";
 
-/* unz_file_info_interntal contain internal info about a file in zipfile*/
+/* unz_file_info64_internal contain internal info about a file in zipfile*/
 typedef struct unz_file_info64_internal_s
 {
     ZPOS64_T offset_curfile;/* relative offset of local header 8 bytes */
@@ -450,7 +450,7 @@ local ZPOS64_T unz64local_SearchCentralDir64(const zlib_filefunc64_32_def* pzlib
     if (unz64local_getLong(pzlib_filefunc_def,filestream,&uL)!=UNZ_OK)
         return CENTRALDIRINVALID;
 
-    /* number of the disk with the start of the zip64 end of  central directory */
+    /* number of the disk with the start of the zip64 end of central directory */
     if (unz64local_getLong(pzlib_filefunc_def,filestream,&uL)!=UNZ_OK)
         return CENTRALDIRINVALID;
     if (uL != 0)
@@ -497,9 +497,9 @@ local unzFile unzOpenInternal(const void *path,
     ZPOS64_T central_pos;
     uLong   uL;
 
-    uLong number_disk;          /* number of the current dist, used for
+    uLong number_disk;          /* number of the current disk, used for
                                    spanning ZIP, unsupported, always 0*/
-    uLong number_disk_with_CD;  /* number the the disk with central dir, used
+    uLong number_disk_with_CD;  /* number the disk with central dir, used
                                    for spanning ZIP, unsupported, always 0*/
     ZPOS64_T number_entry_CD;      /* total number of entries in
                                    the central dir
diff --git a/contrib/minizip/unzip.h b/contrib/minizip/unzip.h
index 14105840f..5cfc9c627 100644
--- a/contrib/minizip/unzip.h
+++ b/contrib/minizip/unzip.h
@@ -306,7 +306,7 @@ extern int ZEXPORT unzGetCurrentFileInfo(unzFile file,
   Get Info about the current file
   if pfile_info!=NULL, the *pfile_info structure will contain some info about
         the current file
-  if szFileName!=NULL, the filemane string will be copied in szFileName
+  if szFileName!=NULL, the filename string will be copied in szFileName
             (fileNameBufferSize is the size of the buffer)
   if extraField!=NULL, the extra field information will be copied in extraField
             (extraFieldBufferSize is the size of the buffer).
diff --git a/contrib/minizip/zip.c b/contrib/minizip/zip.c
index 0446109b2..60bdffac3 100644
--- a/contrib/minizip/zip.c
+++ b/contrib/minizip/zip.c
@@ -575,7 +575,7 @@ local ZPOS64_T zip64local_SearchCentralDir64(const zlib_filefunc64_32_def* pzlib
   if (zip64local_getLong(pzlib_filefunc_def,filestream,&uL)!=ZIP_OK)
     return 0;
 
-  /* number of the disk with the start of the zip64 end of  central directory */
+  /* number of the disk with the start of the zip64 end of central directory */
   if (zip64local_getLong(pzlib_filefunc_def,filestream,&uL)!=ZIP_OK)
     return 0;
   if (uL != 0)
@@ -614,9 +614,9 @@ local int LoadCentralDirectoryRecord(zip64_internal* pziinit) {
   ZPOS64_T central_pos;
   uLong uL;
 
-  uLong number_disk;          /* number of the current dist, used for
+  uLong number_disk;          /* number of the current disk, used for
                               spanning ZIP, unsupported, always 0*/
-  uLong number_disk_with_CD;  /* number the the disk with central dir, used
+  uLong number_disk_with_CD;  /* number of the disk with central dir, used
                               for spanning ZIP, unsupported, always 0*/
   ZPOS64_T number_entry;
   ZPOS64_T number_entry_CD;      /* total number of entries in
@@ -1608,7 +1608,7 @@ extern int ZEXPORT zipCloseFileInZipRaw64(zipFile file, ZPOS64_T uncompressed_si
 
       if((uLong)(datasize + 4) > zi->ci.size_centralExtraFree)
       {
-        // we can not write more data to the buffer that we have room for.
+        // we cannot write more data to the buffer that we have room for.
         return ZIP_BADZIPFILE;
       }
 
@@ -1872,7 +1872,7 @@ extern int ZEXPORT zipClose(zipFile file, const char* global_comment) {
     free_linkedlist(&(zi->central_dir));
 
     pos = centraldir_pos_inzip - zi->add_position_when_writing_offset;
-    if(pos >= 0xffffffff || zi->number_entry > 0xFFFF)
+    if(pos >= 0xffffffff || zi->number_entry >= 0xFFFF)
     {
       ZPOS64_T Zip64EOCDpos = ZTELL64(zi->z_filefunc,zi->filestream);
       Write_Zip64EndOfCentralDirectoryRecord(zi, size_centraldir, centraldir_pos_inzip);
diff --git a/contrib/minizip/zip.h b/contrib/minizip/zip.h
index 5fc084132..3e230d340 100644
--- a/contrib/minizip/zip.h
+++ b/contrib/minizip/zip.h
@@ -177,9 +177,9 @@ extern int ZEXPORT zipOpenNewFileInZip64(zipFile file,
   filename : the filename in zip (if NULL, '-' without quote will be used
   *zipfi contain supplemental information
   if extrafield_local!=NULL and size_extrafield_local>0, extrafield_local
-    contains the extrafield data the the local header
+    contains the extrafield data for the local header
   if extrafield_global!=NULL and size_extrafield_global>0, extrafield_global
-    contains the extrafield data the the local header
+    contains the extrafield data for the global header
   if comment != NULL, comment contain the comment string
   method contain the compression method (0 for store, Z_DEFLATED for deflate)
   level contain the level of compression (can be Z_DEFAULT_COMPRESSION)
diff --git a/contrib/nuget/nuget.csproj b/contrib/nuget/nuget.csproj
index b72cbb67b..68627f034 100644
--- a/contrib/nuget/nuget.csproj
+++ b/contrib/nuget/nuget.csproj
@@ -6,8 +6,8 @@
     <PackageId Condition="$([MSBuild]::IsOSPlatform('Windows'))">$(PackageId).win</PackageId>
     <PackageId Condition="$([MSBuild]::IsOSPlatform('Linux'))">$(PackageId).linux</PackageId>
     <PackageId Condition="$([MSBuild]::IsOSPlatform('OSX'))">$(PackageId).osx</PackageId>
-    <Copyright>(C) 1995-2023 Jean-loup Gailly and Mark Adler</Copyright>
-    <version>1.3.0.1</version>
+    <Copyright>(C) 1995-2024 Jean-loup Gailly and Mark Adler</Copyright>
+    <version>1.3.1</version>
     <PackageDescription>NuGet Package for consuming native builds of zlib into .NET without complexity.</PackageDescription>
     <!--
         Warns about not having any lib or ref assemblies (.NET Assemblies) in those directories.
diff --git a/contrib/pascal/zlibpas.pas b/contrib/pascal/zlibpas.pas
index 1b79ca00a..0cf0e7b82 100644
--- a/contrib/pascal/zlibpas.pas
+++ b/contrib/pascal/zlibpas.pas
@@ -10,7 +10,7 @@
 interface
 
 const
-  ZLIB_VERSION = '1.3.0.1';
+  ZLIB_VERSION = '1.3.1';
   ZLIB_VERNUM  = $12a0;
 
 type
diff --git a/contrib/puff/puff.c b/contrib/puff/puff.c
index 6737ff615..d759825ab 100644
--- a/contrib/puff/puff.c
+++ b/contrib/puff/puff.c
@@ -593,10 +593,10 @@ local int fixed(struct state *s)
  *   provided for each of the literal/length symbols, and for each of the
  *   distance symbols.
  *
- * - If a symbol is not used in the block, this is represented by a zero as
- *   as the code length.  This does not mean a zero-length code, but rather
- *   that no code should be created for this symbol.  There is no way in the
- *   deflate format to represent a zero-length code.
+ * - If a symbol is not used in the block, this is represented by a zero as the
+ *   code length.  This does not mean a zero-length code, but rather that no
+ *   code should be created for this symbol.  There is no way in the deflate
+ *   format to represent a zero-length code.
  *
  * - The maximum number of bits in a code is 15, so the possible lengths for
  *   any code are 1..15.
diff --git a/contrib/vstudio/readme.txt b/contrib/vstudio/readme.txt
index a5000ae7b..061bbc0e2 100644
--- a/contrib/vstudio/readme.txt
+++ b/contrib/vstudio/readme.txt
@@ -1,4 +1,4 @@
-Building instructions for the DLL versions of Zlib 1.3.0.1
+Building instructions for the DLL versions of Zlib 1.3.1
 ========================================================
 
 This directory contains projects that build zlib and minizip using
diff --git a/contrib/vstudio/vc10/zlib.rc b/contrib/vstudio/vc10/zlib.rc
index 75b928396..856bd11f0 100644
--- a/contrib/vstudio/vc10/zlib.rc
+++ b/contrib/vstudio/vc10/zlib.rc
@@ -2,8 +2,8 @@
 
 #define IDR_VERSION1  1
 IDR_VERSION1	VERSIONINFO	MOVEABLE IMPURE LOADONCALL DISCARDABLE
-  FILEVERSION	 1, 3, 0, 1
-  PRODUCTVERSION 1, 3, 0, 1
+  FILEVERSION	 1, 3, 1, 0
+  PRODUCTVERSION 1, 3, 1, 0
   FILEFLAGSMASK	VS_FFI_FILEFLAGSMASK
   FILEFLAGS	0
   FILEOS	VOS_DOS_WINDOWS32
@@ -17,12 +17,12 @@ BEGIN
 
     BEGIN
       VALUE "FileDescription", "zlib data compression and ZIP file I/O library\0"
-      VALUE "FileVersion",	"1.3.0.1\0"
+      VALUE "FileVersion",	"1.3.1\0"
       VALUE "InternalName",	"zlib\0"
       VALUE "OriginalFilename",	"zlibwapi.dll\0"
       VALUE "ProductName",	"ZLib.DLL\0"
       VALUE "Comments","DLL support by Alessandro Iacopetti & Gilles Vollant\0"
-      VALUE "LegalCopyright", "(C) 1995-2023 Jean-loup Gailly & Mark Adler\0"
+      VALUE "LegalCopyright", "(C) 1995-2024 Jean-loup Gailly & Mark Adler\0"
     END
   END
   BLOCK "VarFileInfo"
diff --git a/contrib/vstudio/vc10/zlibvc.def b/contrib/vstudio/vc10/zlibvc.def
index f28aa6c73..3234a02d9 100644
--- a/contrib/vstudio/vc10/zlibvc.def
+++ b/contrib/vstudio/vc10/zlibvc.def
@@ -1,7 +1,7 @@
 LIBRARY
 ; zlib data compression and ZIP file I/O library
 
-VERSION		1.3
+VERSION		1.3.1
 
 EXPORTS
         adler32                                  @1
diff --git a/contrib/vstudio/vc11/zlib.rc b/contrib/vstudio/vc11/zlib.rc
index 75b928396..856bd11f0 100644
--- a/contrib/vstudio/vc11/zlib.rc
+++ b/contrib/vstudio/vc11/zlib.rc
@@ -2,8 +2,8 @@
 
 #define IDR_VERSION1  1
 IDR_VERSION1	VERSIONINFO	MOVEABLE IMPURE LOADONCALL DISCARDABLE
-  FILEVERSION	 1, 3, 0, 1
-  PRODUCTVERSION 1, 3, 0, 1
+  FILEVERSION	 1, 3, 1, 0
+  PRODUCTVERSION 1, 3, 1, 0
   FILEFLAGSMASK	VS_FFI_FILEFLAGSMASK
   FILEFLAGS	0
   FILEOS	VOS_DOS_WINDOWS32
@@ -17,12 +17,12 @@ BEGIN
 
     BEGIN
       VALUE "FileDescription", "zlib data compression and ZIP file I/O library\0"
-      VALUE "FileVersion",	"1.3.0.1\0"
+      VALUE "FileVersion",	"1.3.1\0"
       VALUE "InternalName",	"zlib\0"
       VALUE "OriginalFilename",	"zlibwapi.dll\0"
       VALUE "ProductName",	"ZLib.DLL\0"
       VALUE "Comments","DLL support by Alessandro Iacopetti & Gilles Vollant\0"
-      VALUE "LegalCopyright", "(C) 1995-2023 Jean-loup Gailly & Mark Adler\0"
+      VALUE "LegalCopyright", "(C) 1995-2024 Jean-loup Gailly & Mark Adler\0"
     END
   END
   BLOCK "VarFileInfo"
diff --git a/contrib/vstudio/vc11/zlibvc.def b/contrib/vstudio/vc11/zlibvc.def
index f28aa6c73..3234a02d9 100644
--- a/contrib/vstudio/vc11/zlibvc.def
+++ b/contrib/vstudio/vc11/zlibvc.def
@@ -1,7 +1,7 @@
 LIBRARY
 ; zlib data compression and ZIP file I/O library
 
-VERSION		1.3
+VERSION		1.3.1
 
 EXPORTS
         adler32                                  @1
diff --git a/contrib/vstudio/vc12/zlib.rc b/contrib/vstudio/vc12/zlib.rc
index e54fac43c..a55f341c7 100644
--- a/contrib/vstudio/vc12/zlib.rc
+++ b/contrib/vstudio/vc12/zlib.rc
@@ -2,8 +2,8 @@
 
 #define IDR_VERSION1  1
 IDR_VERSION1	VERSIONINFO	MOVEABLE IMPURE LOADONCALL DISCARDABLE
-  FILEVERSION	 1, 3, 0, 1
-  PRODUCTVERSION 1, 3, 0, 1
+  FILEVERSION	 1, 3, 1, 0
+  PRODUCTVERSION 1, 3, 1, 0
   FILEFLAGSMASK	VS_FFI_FILEFLAGSMASK
   FILEFLAGS	0
   FILEOS	VOS_DOS_WINDOWS32
@@ -17,12 +17,12 @@ BEGIN
 
     BEGIN
       VALUE "FileDescription", "zlib data compression and ZIP file I/O library\0"
-      VALUE "FileVersion",	"1.3.0.1\0"
+      VALUE "FileVersion",	"1.3.1\0"
       VALUE "InternalName",	"zlib\0"
       VALUE "OriginalFilename",	"zlibwapi.dll\0"
       VALUE "ProductName",	"ZLib.DLL\0"
       VALUE "Comments","DLL support by Alessandro Iacopetti & Gilles Vollant\0"
-      VALUE "LegalCopyright", "(C) 1995-2023 Jean-loup Gailly & Mark Adler\0"
+      VALUE "LegalCopyright", "(C) 1995-2024 Jean-loup Gailly & Mark Adler\0"
     END
   END
   BLOCK "VarFileInfo"
diff --git a/contrib/vstudio/vc12/zlibvc.def b/contrib/vstudio/vc12/zlibvc.def
index f28aa6c73..3234a02d9 100644
--- a/contrib/vstudio/vc12/zlibvc.def
+++ b/contrib/vstudio/vc12/zlibvc.def
@@ -1,7 +1,7 @@
 LIBRARY
 ; zlib data compression and ZIP file I/O library
 
-VERSION		1.3
+VERSION		1.3.1
 
 EXPORTS
         adler32                                  @1
diff --git a/contrib/vstudio/vc14/zlib.rc b/contrib/vstudio/vc14/zlib.rc
index e54fac43c..a55f341c7 100644
--- a/contrib/vstudio/vc14/zlib.rc
+++ b/contrib/vstudio/vc14/zlib.rc
@@ -2,8 +2,8 @@
 
 #define IDR_VERSION1  1
 IDR_VERSION1	VERSIONINFO	MOVEABLE IMPURE LOADONCALL DISCARDABLE
-  FILEVERSION	 1, 3, 0, 1
-  PRODUCTVERSION 1, 3, 0, 1
+  FILEVERSION	 1, 3, 1, 0
+  PRODUCTVERSION 1, 3, 1, 0
   FILEFLAGSMASK	VS_FFI_FILEFLAGSMASK
   FILEFLAGS	0
   FILEOS	VOS_DOS_WINDOWS32
@@ -17,12 +17,12 @@ BEGIN
 
     BEGIN
       VALUE "FileDescription", "zlib data compression and ZIP file I/O library\0"
-      VALUE "FileVersion",	"1.3.0.1\0"
+      VALUE "FileVersion",	"1.3.1\0"
       VALUE "InternalName",	"zlib\0"
       VALUE "OriginalFilename",	"zlibwapi.dll\0"
       VALUE "ProductName",	"ZLib.DLL\0"
       VALUE "Comments","DLL support by Alessandro Iacopetti & Gilles Vollant\0"
-      VALUE "LegalCopyright", "(C) 1995-2023 Jean-loup Gailly & Mark Adler\0"
+      VALUE "LegalCopyright", "(C) 1995-2024 Jean-loup Gailly & Mark Adler\0"
     END
   END
   BLOCK "VarFileInfo"
diff --git a/contrib/vstudio/vc14/zlibvc.def b/contrib/vstudio/vc14/zlibvc.def
index f28aa6c73..3234a02d9 100644
--- a/contrib/vstudio/vc14/zlibvc.def
+++ b/contrib/vstudio/vc14/zlibvc.def
@@ -1,7 +1,7 @@
 LIBRARY
 ; zlib data compression and ZIP file I/O library
 
-VERSION		1.3
+VERSION		1.3.1
 
 EXPORTS
         adler32                                  @1
diff --git a/contrib/vstudio/vc17/zlib.rc b/contrib/vstudio/vc17/zlib.rc
index e54fac43c..a55f341c7 100644
--- a/contrib/vstudio/vc17/zlib.rc
+++ b/contrib/vstudio/vc17/zlib.rc
@@ -2,8 +2,8 @@
 
 #define IDR_VERSION1  1
 IDR_VERSION1	VERSIONINFO	MOVEABLE IMPURE LOADONCALL DISCARDABLE
-  FILEVERSION	 1, 3, 0, 1
-  PRODUCTVERSION 1, 3, 0, 1
+  FILEVERSION	 1, 3, 1, 0
+  PRODUCTVERSION 1, 3, 1, 0
   FILEFLAGSMASK	VS_FFI_FILEFLAGSMASK
   FILEFLAGS	0
   FILEOS	VOS_DOS_WINDOWS32
@@ -17,12 +17,12 @@ BEGIN
 
     BEGIN
       VALUE "FileDescription", "zlib data compression and ZIP file I/O library\0"
-      VALUE "FileVersion",	"1.3.0.1\0"
+      VALUE "FileVersion",	"1.3.1\0"
       VALUE "InternalName",	"zlib\0"
       VALUE "OriginalFilename",	"zlibwapi.dll\0"
       VALUE "ProductName",	"ZLib.DLL\0"
       VALUE "Comments","DLL support by Alessandro Iacopetti & Gilles Vollant\0"
-      VALUE "LegalCopyright", "(C) 1995-2023 Jean-loup Gailly & Mark Adler\0"
+      VALUE "LegalCopyright", "(C) 1995-2024 Jean-loup Gailly & Mark Adler\0"
     END
   END
   BLOCK "VarFileInfo"
diff --git a/contrib/vstudio/vc17/zlibvc.def b/contrib/vstudio/vc17/zlibvc.def
index c34923505..53947cc31 100644
--- a/contrib/vstudio/vc17/zlibvc.def
+++ b/contrib/vstudio/vc17/zlibvc.def
@@ -1,7 +1,7 @@
 LIBRARY
 ; zlib data compression and ZIP file I/O library
 
-VERSION		1.3
+VERSION		1.3.1
 
 EXPORTS
         adler32                                  @1
diff --git a/contrib/vstudio/vc9/zlib.rc b/contrib/vstudio/vc9/zlib.rc
index 75b928396..856bd11f0 100644
--- a/contrib/vstudio/vc9/zlib.rc
+++ b/contrib/vstudio/vc9/zlib.rc
@@ -2,8 +2,8 @@
 
 #define IDR_VERSION1  1
 IDR_VERSION1	VERSIONINFO	MOVEABLE IMPURE LOADONCALL DISCARDABLE
-  FILEVERSION	 1, 3, 0, 1
-  PRODUCTVERSION 1, 3, 0, 1
+  FILEVERSION	 1, 3, 1, 0
+  PRODUCTVERSION 1, 3, 1, 0
   FILEFLAGSMASK	VS_FFI_FILEFLAGSMASK
   FILEFLAGS	0
   FILEOS	VOS_DOS_WINDOWS32
@@ -17,12 +17,12 @@ BEGIN
 
     BEGIN
       VALUE "FileDescription", "zlib data compression and ZIP file I/O library\0"
-      VALUE "FileVersion",	"1.3.0.1\0"
+      VALUE "FileVersion",	"1.3.1\0"
       VALUE "InternalName",	"zlib\0"
       VALUE "OriginalFilename",	"zlibwapi.dll\0"
       VALUE "ProductName",	"ZLib.DLL\0"
       VALUE "Comments","DLL support by Alessandro Iacopetti & Gilles Vollant\0"
-      VALUE "LegalCopyright", "(C) 1995-2023 Jean-loup Gailly & Mark Adler\0"
+      VALUE "LegalCopyright", "(C) 1995-2024 Jean-loup Gailly & Mark Adler\0"
     END
   END
   BLOCK "VarFileInfo"
diff --git a/contrib/vstudio/vc9/zlibvc.def b/contrib/vstudio/vc9/zlibvc.def
index f28aa6c73..3234a02d9 100644
--- a/contrib/vstudio/vc9/zlibvc.def
+++ b/contrib/vstudio/vc9/zlibvc.def
@@ -1,7 +1,7 @@
 LIBRARY
 ; zlib data compression and ZIP file I/O library
 
-VERSION		1.3
+VERSION		1.3.1
 
 EXPORTS
         adler32                                  @1
diff --git a/deflate.c b/deflate.c
index 5e72cd926..012ea8148 100644
--- a/deflate.c
+++ b/deflate.c
@@ -1,5 +1,5 @@
 /* deflate.c -- compress data using the deflation algorithm
- * Copyright (C) 1995-2023 Jean-loup Gailly and Mark Adler
+ * Copyright (C) 1995-2024 Jean-loup Gailly and Mark Adler
  * For conditions of distribution and use, see copyright notice in zlib.h
  */
 
@@ -52,7 +52,7 @@
 #include "deflate.h"
 
 const char deflate_copyright[] =
-   " deflate 1.3.0.1 Copyright 1995-2023 Jean-loup Gailly and Mark Adler ";
+   " deflate 1.3.1 Copyright 1995-2024 Jean-loup Gailly and Mark Adler ";
 /*
   If you use the zlib library in a product, an acknowledgment is welcome
   in the documentation of your product. If for some reason you cannot
@@ -493,7 +493,7 @@ int ZEXPORT deflateInit2_(z_streamp strm, int level, int method,
      * symbols from which it is being constructed.
      */
 
-    s->pending_buf = (uchf *) ZALLOC(strm, s->lit_bufsize, 4);
+    s->pending_buf = (uchf *) ZALLOC(strm, s->lit_bufsize, LIT_BUFS);
     s->pending_buf_size = (ulg)s->lit_bufsize * 4;
 
     if (s->window == Z_NULL || s->prev == Z_NULL || s->head == Z_NULL ||
@@ -503,8 +503,14 @@ int ZEXPORT deflateInit2_(z_streamp strm, int level, int method,
         deflateEnd (strm);
         return Z_MEM_ERROR;
     }
+#ifdef LIT_MEM
+    s->d_buf = (ushf *)(s->pending_buf + (s->lit_bufsize << 1));
+    s->l_buf = s->pending_buf + (s->lit_bufsize << 2);
+    s->sym_end = s->lit_bufsize - 1;
+#else
     s->sym_buf = s->pending_buf + s->lit_bufsize;
     s->sym_end = (s->lit_bufsize - 1) * 3;
+#endif
     /* We avoid equality with lit_bufsize*3 because of wraparound at 64K
      * on 16 bit machines and because stored blocks are restricted to
      * 64K-1 bytes.
@@ -720,9 +726,15 @@ int ZEXPORT deflatePrime(z_streamp strm, int bits, int value) {
 
     if (deflateStateCheck(strm)) return Z_STREAM_ERROR;
     s = strm->state;
+#ifdef LIT_MEM
+    if (bits < 0 || bits > 16 ||
+        (uchf *)s->d_buf < s->pending_out + ((Buf_size + 7) >> 3))
+        return Z_BUF_ERROR;
+#else
     if (bits < 0 || bits > 16 ||
         s->sym_buf < s->pending_out + ((Buf_size + 7) >> 3))
         return Z_BUF_ERROR;
+#endif
     do {
         put = Buf_size - s->bi_valid;
         if (put > bits)
@@ -1294,7 +1306,7 @@ int ZEXPORT deflateCopy(z_streamp dest, z_streamp source) {
     ds->window = (Bytef *) ZALLOC(dest, ds->w_size, 2*sizeof(Byte));
     ds->prev   = (Posf *)  ZALLOC(dest, ds->w_size, sizeof(Pos));
     ds->head   = (Posf *)  ZALLOC(dest, ds->hash_size, sizeof(Pos));
-    ds->pending_buf = (uchf *) ZALLOC(dest, ds->lit_bufsize, 4);
+    ds->pending_buf = (uchf *) ZALLOC(dest, ds->lit_bufsize, LIT_BUFS);
 
     if (ds->window == Z_NULL || ds->prev == Z_NULL || ds->head == Z_NULL ||
         ds->pending_buf == Z_NULL) {
@@ -1305,10 +1317,15 @@ int ZEXPORT deflateCopy(z_streamp dest, z_streamp source) {
     zmemcpy(ds->window, ss->window, ds->w_size * 2 * sizeof(Byte));
     zmemcpy((voidpf)ds->prev, (voidpf)ss->prev, ds->w_size * sizeof(Pos));
     zmemcpy((voidpf)ds->head, (voidpf)ss->head, ds->hash_size * sizeof(Pos));
-    zmemcpy(ds->pending_buf, ss->pending_buf, (uInt)ds->pending_buf_size);
+    zmemcpy(ds->pending_buf, ss->pending_buf, ds->lit_bufsize * LIT_BUFS);
 
     ds->pending_out = ds->pending_buf + (ss->pending_out - ss->pending_buf);
+#ifdef LIT_MEM
+    ds->d_buf = (ushf *)(ds->pending_buf + (ds->lit_bufsize << 1));
+    ds->l_buf = ds->pending_buf + (ds->lit_bufsize << 2);
+#else
     ds->sym_buf = ds->pending_buf + ds->lit_bufsize;
+#endif
 
     ds->l_desc.dyn_tree = ds->dyn_ltree;
     ds->d_desc.dyn_tree = ds->dyn_dtree;
@@ -1539,13 +1556,21 @@ local uInt longest_match(deflate_state *s, IPos cur_match) {
  */
 local void check_match(deflate_state *s, IPos start, IPos match, int length) {
     /* check that the match is indeed a match */
-    if (zmemcmp(s->window + match,
-                s->window + start, length) != EQUAL) {
-        fprintf(stderr, " start %u, match %u, length %d\n",
-                start, match, length);
+    Bytef *back = s->window + (int)match, *here = s->window + start;
+    IPos len = length;
+    if (match == (IPos)-1) {
+        /* match starts one byte before the current window -- just compare the
+           subsequent length-1 bytes */
+        back++;
+        here++;
+        len--;
+    }
+    if (zmemcmp(back, here, len) != EQUAL) {
+        fprintf(stderr, " start %u, match %d, length %d\n",
+                start, (int)match, length);
         do {
-            fprintf(stderr, "%c%c", s->window[match++], s->window[start++]);
-        } while (--length != 0);
+            fprintf(stderr, "(%02x %02x)", *back++, *here++);
+        } while (--len != 0);
         z_error("invalid match");
     }
     if (z_verbose > 1) {
diff --git a/deflate.h b/deflate.h
index 869679142..300c6ada6 100644
--- a/deflate.h
+++ b/deflate.h
@@ -1,5 +1,5 @@
 /* deflate.h -- internal compression state
- * Copyright (C) 1995-2018 Jean-loup Gailly
+ * Copyright (C) 1995-2024 Jean-loup Gailly
  * For conditions of distribution and use, see copyright notice in zlib.h
  */
 
@@ -23,6 +23,10 @@
 #  define GZIP
 #endif
 
+/* define LIT_MEM to slightly increase the speed of deflate (order 1% to 2%) at
+   the cost of a larger memory footprint */
+/* #define LIT_MEM */
+
 /* ===========================================================================
  * Internal compression state.
  */
@@ -217,7 +221,14 @@ typedef struct internal_state {
     /* Depth of each subtree used as tie breaker for trees of equal frequency
      */
 
+#ifdef LIT_MEM
+#   define LIT_BUFS 5
+    ushf *d_buf;          /* buffer for distances */
+    uchf *l_buf;          /* buffer for literals/lengths */
+#else
+#   define LIT_BUFS 4
     uchf *sym_buf;        /* buffer for distances and literals/lengths */
+#endif
 
     uInt  lit_bufsize;
     /* Size of match buffer for literals/lengths.  There are 4 reasons for
@@ -239,7 +250,7 @@ typedef struct internal_state {
      *   - I can't count above 4
      */
 
-    uInt sym_next;      /* running index in sym_buf */
+    uInt sym_next;      /* running index in symbol buffer */
     uInt sym_end;       /* symbol table full when sym_next reaches this */
 
     ulg opt_len;        /* bit length of current block with optimal trees */
@@ -318,6 +329,25 @@ void ZLIB_INTERNAL _tr_stored_block(deflate_state *s, charf *buf,
   extern const uch ZLIB_INTERNAL _dist_code[];
 #endif
 
+#ifdef LIT_MEM
+# define _tr_tally_lit(s, c, flush) \
+  { uch cc = (c); \
+    s->d_buf[s->sym_next] = 0; \
+    s->l_buf[s->sym_next++] = cc; \
+    s->dyn_ltree[cc].Freq++; \
+    flush = (s->sym_next == s->sym_end); \
+   }
+# define _tr_tally_dist(s, distance, length, flush) \
+  { uch len = (uch)(length); \
+    ush dist = (ush)(distance); \
+    s->d_buf[s->sym_next] = dist; \
+    s->l_buf[s->sym_next++] = len; \
+    dist--; \
+    s->dyn_ltree[_length_code[len]+LITERALS+1].Freq++; \
+    s->dyn_dtree[d_code(dist)].Freq++; \
+    flush = (s->sym_next == s->sym_end); \
+  }
+#else
 # define _tr_tally_lit(s, c, flush) \
   { uch cc = (c); \
     s->sym_buf[s->sym_next++] = 0; \
@@ -337,6 +367,7 @@ void ZLIB_INTERNAL _tr_stored_block(deflate_state *s, charf *buf,
     s->dyn_dtree[d_code(dist)].Freq++; \
     flush = (s->sym_next == s->sym_end); \
   }
+#endif
 #else
 # define _tr_tally_lit(s, c, flush) flush = _tr_tally(s, 0, c)
 # define _tr_tally_dist(s, distance, length, flush) \
diff --git a/doc/algorithm.txt b/doc/algorithm.txt
index c97f49502..029e5a313 100644
--- a/doc/algorithm.txt
+++ b/doc/algorithm.txt
@@ -77,7 +77,7 @@ table took no time (and if you had infinite memory), then there would only
 be a first level table to cover all the way to the longest code.  However,
 building the table ends up taking a lot longer for more bits since short
 codes are replicated many times in such a table.  What inflate() does is
-simply to make the number of bits in the first table a variable, and  then
+simply to make the number of bits in the first table a variable, and then
 to set that variable for the maximum speed.
 
 For inflate, which has 286 possible codes for the literal/length tree, the size
diff --git a/examples/gzlog.c b/examples/gzlog.c
index b977802dd..da1b02e73 100644
--- a/examples/gzlog.c
+++ b/examples/gzlog.c
@@ -212,8 +212,8 @@
      to the appropriate recovery below.  If there is no foo.add file, provide
      a zero data length to the recovery.  In that case, the append recovery
      restores the foo.gz to the previous compressed + uncompressed data state.
-     For the the compress recovery, a missing foo.add file results in foo.gz
-     being restored to the previous compressed-only data state.
+     For the compress recovery, a missing foo.add file results in foo.gz being
+     restored to the previous compressed-only data state.
    - Append recovery:
      - Pick up append at + step above
    - Compress recovery:
diff --git a/examples/zran.c b/examples/zran.c
index 32c93686c..d3135955b 100644
--- a/examples/zran.c
+++ b/examples/zran.c
@@ -267,7 +267,7 @@ static inline void append_bits(unsigned value, int bits,
     }
 }
 
-// Insert enough bits in the form of empty deflate blocks in front of the the
+// Insert enough bits in the form of empty deflate blocks in front of the
 // low bits bits of value, in order to bring the sequence to a byte boundary.
 // Then feed that to inflate(). This does what inflatePrime() does, except that
 // a negative value of bits is not supported. bits must be in 0..16. If the
diff --git a/gzguts.h b/gzguts.h
index f9375047e..eba72085b 100644
--- a/gzguts.h
+++ b/gzguts.h
@@ -1,5 +1,5 @@
 /* gzguts.h -- zlib internal header definitions for gz* operations
- * Copyright (C) 2004-2019 Mark Adler
+ * Copyright (C) 2004-2024 Mark Adler
  * For conditions of distribution and use, see copyright notice in zlib.h
  */
 
@@ -210,9 +210,5 @@ char ZLIB_INTERNAL *gz_strwinerror(DWORD error);
 /* GT_OFF(x), where x is an unsigned value, is true if x > maximum z_off64_t
    value -- needed when comparing unsigned to z_off64_t, which is signed
    (possible z_off64_t types off_t, off64_t, and long are all signed) */
-#ifdef INT_MAX
-#  define GT_OFF(x) (sizeof(int) == sizeof(z_off64_t) && (x) > INT_MAX)
-#else
 unsigned ZLIB_INTERNAL gz_intmax(void);
-#  define GT_OFF(x) (sizeof(int) == sizeof(z_off64_t) && (x) > gz_intmax())
-#endif
+#define GT_OFF(x) (sizeof(int) == sizeof(z_off64_t) && (x) > gz_intmax())
diff --git a/gzlib.c b/gzlib.c
index 29fc4486f..983153cc8 100644
--- a/gzlib.c
+++ b/gzlib.c
@@ -1,5 +1,5 @@
 /* gzlib.c -- zlib functions common to reading and writing gzip files
- * Copyright (C) 2004-2019 Mark Adler
+ * Copyright (C) 2004-2024 Mark Adler
  * For conditions of distribution and use, see copyright notice in zlib.h
  */
 
@@ -563,20 +563,20 @@ void ZLIB_INTERNAL gz_error(gz_statep state, int err, const char *msg) {
 #endif
 }
 
-#ifndef INT_MAX
 /* portably return maximum value for an int (when limits.h presumed not
    available) -- we need to do this to cover cases where 2's complement not
    used, since C standard permits 1's complement and sign-bit representations,
    otherwise we could just use ((unsigned)-1) >> 1 */
 unsigned ZLIB_INTERNAL gz_intmax(void) {
-    unsigned p, q;
-
-    p = 1;
+#ifdef INT_MAX
+    return INT_MAX;
+#else
+    unsigned p = 1, q;
     do {
         q = p;
         p <<= 1;
         p++;
     } while (p > q);
     return q >> 1;
-}
 #endif
+}
diff --git a/inflate.c b/inflate.c
index b0757a9b2..94ecff015 100644
--- a/inflate.c
+++ b/inflate.c
@@ -1387,7 +1387,7 @@ int ZEXPORT inflateSync(z_streamp strm) {
     /* if first time, start search in bit buffer */
     if (state->mode != SYNC) {
         state->mode = SYNC;
-        state->hold <<= state->bits & 7;
+        state->hold >>= state->bits & 7;
         state->bits -= state->bits & 7;
         len = 0;
         while (state->bits >= 8) {
diff --git a/inftrees.c b/inftrees.c
index 73d5a7769..98cfe1644 100644
--- a/inftrees.c
+++ b/inftrees.c
@@ -1,5 +1,5 @@
 /* inftrees.c -- generate Huffman trees for efficient decoding
- * Copyright (C) 1995-2023 Mark Adler
+ * Copyright (C) 1995-2024 Mark Adler
  * For conditions of distribution and use, see copyright notice in zlib.h
  */
 
@@ -9,7 +9,7 @@
 #define MAXBITS 15
 
 const char inflate_copyright[] =
-   " inflate 1.3.0.1 Copyright 1995-2023 Mark Adler ";
+   " inflate 1.3.1 Copyright 1995-2024 Mark Adler ";
 /*
   If you use the zlib library in a product, an acknowledgment is welcome
   in the documentation of your product. If for some reason you cannot
@@ -57,7 +57,7 @@ int ZLIB_INTERNAL inflate_table(codetype type, unsigned short FAR *lens,
         35, 43, 51, 59, 67, 83, 99, 115, 131, 163, 195, 227, 258, 0, 0};
     static const unsigned short lext[31] = { /* Length codes 257..285 extra */
         16, 16, 16, 16, 16, 16, 16, 16, 17, 17, 17, 17, 18, 18, 18, 18,
-        19, 19, 19, 19, 20, 20, 20, 20, 21, 21, 21, 21, 16, 70, 200};
+        19, 19, 19, 19, 20, 20, 20, 20, 21, 21, 21, 21, 16, 203, 77};
     static const unsigned short dbase[32] = { /* Distance codes 0..29 base */
         1, 2, 3, 4, 5, 7, 9, 13, 17, 25, 33, 49, 65, 97, 129, 193,
         257, 385, 513, 769, 1025, 1537, 2049, 3073, 4097, 6145,
diff --git a/inftrees.h b/inftrees.h
index a10712d8c..396f74b5d 100644
--- a/inftrees.h
+++ b/inftrees.h
@@ -41,8 +41,8 @@ typedef struct {
    examples/enough.c found in the zlib distribution.  The arguments to that
    program are the number of symbols, the initial root table size, and the
    maximum bit length of a code.  "enough 286 9 15" for literal/length codes
-   returns returns 852, and "enough 30 6 15" for distance codes returns 592.
-   The initial root table size (9 or 6) is found in the fifth argument of the
+   returns 852, and "enough 30 6 15" for distance codes returns 592. The
+   initial root table size (9 or 6) is found in the fifth argument of the
    inflate_table() calls in inflate.c and infback.c.  If the root table size is
    changed, then these maximum sizes would be need to be recalculated and
    updated. */
diff --git a/old/visual-basic.txt b/old/visual-basic.txt
index 57efe5812..3c8d2a42d 100644
--- a/old/visual-basic.txt
+++ b/old/visual-basic.txt
@@ -115,7 +115,7 @@ SUCCESS Then
         ReDim Preserve bytaryCpr(lngCprSiz - 1)
         Open strCprPth For Binary Access Write As #1
             Put #1, , bytaryCpr()
-            Put #1, , lngOriSiz 'Add the the original size value to the end
+            Put #1, , lngOriSiz 'Add the original size value to the end
 (last 4 bytes)
         Close #1
     Else
diff --git a/os400/README400 b/os400/README400
index 33492f273..30ed5a12c 100644
--- a/os400/README400
+++ b/os400/README400
@@ -1,4 +1,4 @@
-        ZLIB version 1.3.0.1 for OS/400 installation instructions
+        ZLIB version 1.3.1 for OS/400 installation instructions
 
 1) Download and unpack the zlib tarball to some IFS directory.
    (i.e.: /path/to/the/zlib/ifs/source/directory)
diff --git a/os400/zlib.inc b/os400/zlib.inc
index 88b243a4d..744729ab9 100644
--- a/os400/zlib.inc
+++ b/os400/zlib.inc
@@ -1,7 +1,7 @@
       *  ZLIB.INC - Interface to the general purpose compression library
       *
       *  ILE RPG400 version by Patrick Monnerat, DATASPHERE.
-      *  Version 1.3.0.1
+      *  Version 1.3.1
       *
       *
       *  WARNING:
@@ -22,14 +22,14 @@
       *
       *  Versioning information.
       *
-     D ZLIB_VERSION    C                   '1.3.0.1'
+     D ZLIB_VERSION    C                   '1.3.1'
      D ZLIB_VERNUM     C                   X'12a0'
      D ZLIB_VER_MAJOR  C                   1
      D ZLIB_VER_MINOR  C                   3
      D ZLIB_VER_REVISION...
-     D                 C                   0
-     D ZLIB_VER_SUBREVISION...
      D                 C                   1
+     D ZLIB_VER_SUBREVISION...
+     D                 C                   0
       *
       *  Other equates.
       *
diff --git a/qnx/package.qpg b/qnx/package.qpg
index 88343ad2a..4877e0ef0 100644
--- a/qnx/package.qpg
+++ b/qnx/package.qpg
@@ -25,10 +25,10 @@
       <QPG:Files>
          <QPG:Add file="../zconf.h" install="/opt/include/" user="root:sys" permission="644"/>
          <QPG:Add file="../zlib.h" install="/opt/include/" user="root:sys" permission="644"/>
-         <QPG:Add file="../libz.so.1.3.0.1" install="/opt/lib/" user="root:bin" permission="644"/>
-         <QPG:Add file="libz.so" install="/opt/lib/" component="dev" filetype="symlink" linkto="libz.so.1.3.0.1"/>
-         <QPG:Add file="libz.so.1" install="/opt/lib/" filetype="symlink" linkto="libz.so.1.3.0.1"/>
-         <QPG:Add file="../libz.so.1.3.0.1" install="/opt/lib/" component="slib"/>
+         <QPG:Add file="../libz.so.1.3.1" install="/opt/lib/" user="root:bin" permission="644"/>
+         <QPG:Add file="libz.so" install="/opt/lib/" component="dev" filetype="symlink" linkto="libz.so.1.3.1"/>
+         <QPG:Add file="libz.so.1" install="/opt/lib/" filetype="symlink" linkto="libz.so.1.3.1"/>
+         <QPG:Add file="../libz.so.1.3.1" install="/opt/lib/" component="slib"/>
       </QPG:Files>
 
       <QPG:PackageFilter>
@@ -63,7 +63,7 @@
             </QPM:ProductDescription>
 
             <QPM:ReleaseDescription>
-               <QPM:ReleaseVersion>1.3.0.1</QPM:ReleaseVersion>
+               <QPM:ReleaseVersion>1.3.1</QPM:ReleaseVersion>
                <QPM:ReleaseUrgency>Medium</QPM:ReleaseUrgency>
                <QPM:ReleaseStability>Stable</QPM:ReleaseStability>
                <QPM:ReleaseNoteMinor></QPM:ReleaseNoteMinor>
diff --git a/test/example.c b/test/example.c
index 582a17a3c..c3521dd59 100644
--- a/test/example.c
+++ b/test/example.c
@@ -36,12 +36,12 @@ static uLong dictId;    /* Adler32 value of the dictionary */
 
 #ifdef Z_SOLO
 
-void *myalloc(void *q, unsigned n, unsigned m) {
+static void *myalloc(void *q, unsigned n, unsigned m) {
     (void)q;
     return calloc(n, m);
 }
 
-void myfree(void *q, void *p) {
+static void myfree(void *q, void *p) {
     (void)q;
     free(p);
 }
@@ -57,7 +57,7 @@ static free_func zfree = (free_func)0;
 /* ===========================================================================
  * Test compress() and uncompress()
  */
-void test_compress(Byte *compr, uLong comprLen, Byte *uncompr,
+static void test_compress(Byte *compr, uLong comprLen, Byte *uncompr,
                    uLong uncomprLen) {
     int err;
     uLong len = (uLong)strlen(hello)+1;
@@ -81,7 +81,7 @@ void test_compress(Byte *compr, uLong comprLen, Byte *uncompr,
 /* ===========================================================================
  * Test read/write of .gz files
  */
-void test_gzio(const char *fname, Byte *uncompr, uLong uncomprLen) {
+static void test_gzio(const char *fname, Byte *uncompr, uLong uncomprLen) {
 #ifdef NO_GZCOMPRESS
     fprintf(stderr, "NO_GZCOMPRESS -- gz* functions cannot compress\n");
 #else
@@ -163,7 +163,7 @@ void test_gzio(const char *fname, Byte *uncompr, uLong uncomprLen) {
 /* ===========================================================================
  * Test deflate() with small buffers
  */
-void test_deflate(Byte *compr, uLong comprLen) {
+static void test_deflate(Byte *compr, uLong comprLen) {
     z_stream c_stream; /* compression stream */
     int err;
     uLong len = (uLong)strlen(hello)+1;
@@ -198,7 +198,7 @@ void test_deflate(Byte *compr, uLong comprLen) {
 /* ===========================================================================
  * Test inflate() with small buffers
  */
-void test_inflate(Byte *compr, uLong comprLen, Byte *uncompr,
+static void test_inflate(Byte *compr, uLong comprLen, Byte *uncompr,
                   uLong uncomprLen) {
     int err;
     z_stream d_stream; /* decompression stream */
@@ -237,7 +237,7 @@ void test_inflate(Byte *compr, uLong comprLen, Byte *uncompr,
 /* ===========================================================================
  * Test deflate() with large buffers and dynamic change of compression level
  */
-void test_large_deflate(Byte *compr, uLong comprLen, Byte *uncompr,
+static void test_large_deflate(Byte *compr, uLong comprLen, Byte *uncompr,
                         uLong uncomprLen) {
     z_stream c_stream; /* compression stream */
     int err;
@@ -290,7 +290,7 @@ void test_large_deflate(Byte *compr, uLong comprLen, Byte *uncompr,
 /* ===========================================================================
  * Test inflate() with large buffers
  */
-void test_large_inflate(Byte *compr, uLong comprLen, Byte *uncompr,
+static void test_large_inflate(Byte *compr, uLong comprLen, Byte *uncompr,
                         uLong uncomprLen) {
     int err;
     z_stream d_stream; /* decompression stream */
@@ -329,7 +329,7 @@ void test_large_inflate(Byte *compr, uLong comprLen, Byte *uncompr,
 /* ===========================================================================
  * Test deflate() with full flush
  */
-void test_flush(Byte *compr, uLong *comprLen) {
+static void test_flush(Byte *compr, uLong *comprLen) {
     z_stream c_stream; /* compression stream */
     int err;
     uInt len = (uInt)strlen(hello)+1;
@@ -364,7 +364,8 @@ void test_flush(Byte *compr, uLong *comprLen) {
 /* ===========================================================================
  * Test inflateSync()
  */
-void test_sync(Byte *compr, uLong comprLen, Byte *uncompr, uLong uncomprLen) {
+static void test_sync(Byte *compr, uLong comprLen, Byte *uncompr,
+                      uLong uncomprLen) {
     int err;
     z_stream d_stream; /* decompression stream */
 
@@ -404,7 +405,7 @@ void test_sync(Byte *compr, uLong comprLen, Byte *uncompr, uLong uncomprLen) {
 /* ===========================================================================
  * Test deflate() with preset dictionary
  */
-void test_dict_deflate(Byte *compr, uLong comprLen) {
+static void test_dict_deflate(Byte *compr, uLong comprLen) {
     z_stream c_stream; /* compression stream */
     int err;
 
@@ -438,7 +439,7 @@ void test_dict_deflate(Byte *compr, uLong comprLen) {
 /* ===========================================================================
  * Test inflate() with a preset dictionary
  */
-void test_dict_inflate(Byte *compr, uLong comprLen, Byte *uncompr,
+static void test_dict_inflate(Byte *compr, uLong comprLen, Byte *uncompr,
                        uLong uncomprLen) {
     int err;
     z_stream d_stream; /* decompression stream */
diff --git a/test/minigzip.c b/test/minigzip.c
index 8a21ddfb5..134e10e6c 100644
--- a/test/minigzip.c
+++ b/test/minigzip.c
@@ -149,12 +149,12 @@ static void pwinerror (s)
 #  include <unistd.h>       /* for unlink() */
 #endif
 
-void *myalloc(void *q, unsigned n, unsigned m) {
+static void *myalloc(void *q, unsigned n, unsigned m) {
     (void)q;
     return calloc(n, m);
 }
 
-void myfree(void *q, void *p) {
+static void myfree(void *q, void *p) {
     (void)q;
     free(p);
 }
@@ -167,7 +167,7 @@ typedef struct gzFile_s {
     z_stream strm;
 } *gzFile;
 
-gzFile gz_open(const char *path, int fd, const char *mode) {
+static gzFile gz_open(const char *path, int fd, const char *mode) {
     gzFile gz;
     int ret;
 
@@ -201,15 +201,15 @@ gzFile gz_open(const char *path, int fd, const char *mode) {
     return gz;
 }
 
-gzFile gzopen(const char *path, const char *mode) {
+static gzFile gzopen(const char *path, const char *mode) {
     return gz_open(path, -1, mode);
 }
 
-gzFile gzdopen(int fd, const char *mode) {
+static gzFile gzdopen(int fd, const char *mode) {
     return gz_open(NULL, fd, mode);
 }
 
-int gzwrite(gzFile gz, const void *buf, unsigned len) {
+static int gzwrite(gzFile gz, const void *buf, unsigned len) {
     z_stream *strm;
     unsigned char out[BUFLEN];
 
@@ -227,7 +227,7 @@ int gzwrite(gzFile gz, const void *buf, unsigned len) {
     return len;
 }
 
-int gzread(gzFile gz, void *buf, unsigned len) {
+static int gzread(gzFile gz, void *buf, unsigned len) {
     int ret;
     unsigned got;
     unsigned char in[1];
@@ -258,7 +258,7 @@ int gzread(gzFile gz, void *buf, unsigned len) {
     return len - strm->avail_out;
 }
 
-int gzclose(gzFile gz) {
+static int gzclose(gzFile gz) {
     z_stream *strm;
     unsigned char out[BUFLEN];
 
@@ -283,7 +283,7 @@ int gzclose(gzFile gz) {
     return Z_OK;
 }
 
-const char *gzerror(gzFile gz, int *err) {
+static const char *gzerror(gzFile gz, int *err) {
     *err = gz->err;
     return gz->msg;
 }
@@ -295,7 +295,7 @@ static char *prog;
 /* ===========================================================================
  * Display error message and exit
  */
-void error(const char *msg) {
+static void error(const char *msg) {
     fprintf(stderr, "%s: %s\n", prog, msg);
     exit(1);
 }
@@ -303,9 +303,9 @@ void error(const char *msg) {
 #ifdef USE_MMAP /* MMAP version, Miguel Albrecht <malbrech@eso.org> */
 
 /* Try compressing the input file at once using mmap. Return Z_OK if
- * if success, Z_ERRNO otherwise.
+ * success, Z_ERRNO otherwise.
  */
-int gz_compress_mmap(FILE *in, gzFile out) {
+static int gz_compress_mmap(FILE *in, gzFile out) {
     int len;
     int err;
     int ifd = fileno(in);
@@ -338,7 +338,7 @@ int gz_compress_mmap(FILE *in, gzFile out) {
  * Compress input to output then close both files.
  */
 
-void gz_compress(FILE *in, gzFile out) {
+static void gz_compress(FILE *in, gzFile out) {
     local char buf[BUFLEN];
     int len;
     int err;
@@ -366,7 +366,7 @@ void gz_compress(FILE *in, gzFile out) {
 /* ===========================================================================
  * Uncompress input to output then close both files.
  */
-void gz_uncompress(gzFile in, FILE *out) {
+static void gz_uncompress(gzFile in, FILE *out) {
     local char buf[BUFLEN];
     int len;
     int err;
@@ -390,7 +390,7 @@ void gz_uncompress(gzFile in, FILE *out) {
  * Compress the given file: create a corresponding .gz file and remove the
  * original.
  */
-void file_compress(char *file, char *mode) {
+static void file_compress(char *file, char *mode) {
     local char outfile[MAX_NAME_LEN];
     FILE  *in;
     gzFile out;
@@ -426,7 +426,7 @@ void file_compress(char *file, char *mode) {
 /* ===========================================================================
  * Uncompress the given file and remove the original.
  */
-void file_uncompress(char *file) {
+static void file_uncompress(char *file) {
     local char buf[MAX_NAME_LEN];
     char *infile, *outfile;
     FILE  *out;
diff --git a/treebuild.xml b/treebuild.xml
index 8bac3f73b..930b00be4 100644
--- a/treebuild.xml
+++ b/treebuild.xml
@@ -1,6 +1,6 @@
 <?xml version="1.0" ?>
-<package name="zlib" version="1.3.0.1">
-    <library name="zlib" dlversion="1.3.0.1" dlname="z">
+<package name="zlib" version="1.3.1">
+    <library name="zlib" dlversion="1.3.1" dlname="z">
 	<property name="description"> zip compression library </property>
 	<property name="include-target-dir" value="$(@PACKAGE/install-includedir)" />
 
diff --git a/trees.c b/trees.c
index 8dbdc40ba..6a523ef34 100644
--- a/trees.c
+++ b/trees.c
@@ -1,5 +1,5 @@
 /* trees.c -- output deflated data using Huffman coding
- * Copyright (C) 1995-2021 Jean-loup Gailly
+ * Copyright (C) 1995-2024 Jean-loup Gailly
  * detect_data_type() function provided freely by Cosmin Truta, 2006
  * For conditions of distribution and use, see copyright notice in zlib.h
  */
@@ -899,14 +899,19 @@ local void compress_block(deflate_state *s, const ct_data *ltree,
                           const ct_data *dtree) {
     unsigned dist;      /* distance of matched string */
     int lc;             /* match length or unmatched char (if dist == 0) */
-    unsigned sx = 0;    /* running index in sym_buf */
+    unsigned sx = 0;    /* running index in symbol buffers */
     unsigned code;      /* the code to send */
     int extra;          /* number of extra bits to send */
 
     if (s->sym_next != 0) do {
+#ifdef LIT_MEM
+        dist = s->d_buf[sx];
+        lc = s->l_buf[sx++];
+#else
         dist = s->sym_buf[sx++] & 0xff;
         dist += (unsigned)(s->sym_buf[sx++] & 0xff) << 8;
         lc = s->sym_buf[sx++];
+#endif
         if (dist == 0) {
             send_code(s, lc, ltree); /* send a literal byte */
             Tracecv(isgraph(lc), (stderr," '%c' ", lc));
@@ -931,8 +936,12 @@ local void compress_block(deflate_state *s, const ct_data *ltree,
             }
         } /* literal or match pair ? */
 
-        /* Check that the overlay between pending_buf and sym_buf is ok: */
+        /* Check for no overlay of pending_buf on needed symbols */
+#ifdef LIT_MEM
+        Assert(s->pending < 2 * (s->lit_bufsize + sx), "pendingBuf overflow");
+#else
         Assert(s->pending < s->lit_bufsize + sx, "pendingBuf overflow");
+#endif
 
     } while (sx < s->sym_next);
 
@@ -1082,9 +1091,14 @@ void ZLIB_INTERNAL _tr_flush_block(deflate_state *s, charf *buf,
  * the current block must be flushed.
  */
 int ZLIB_INTERNAL _tr_tally(deflate_state *s, unsigned dist, unsigned lc) {
+#ifdef LIT_MEM
+    s->d_buf[s->sym_next] = (ush)dist;
+    s->l_buf[s->sym_next++] = (uch)lc;
+#else
     s->sym_buf[s->sym_next++] = (uch)dist;
     s->sym_buf[s->sym_next++] = (uch)(dist >> 8);
     s->sym_buf[s->sym_next++] = (uch)lc;
+#endif
     if (dist == 0) {
         /* lc is the unmatched char */
         s->dyn_ltree[lc].Freq++;
diff --git a/win32/DLL_FAQ.txt b/win32/DLL_FAQ.txt
index 12c009018..d8cf5f31e 100644
--- a/win32/DLL_FAQ.txt
+++ b/win32/DLL_FAQ.txt
@@ -3,7 +3,7 @@
 
 
 This document describes the design, the rationale, and the usage
-of the official DLL build of zlib, named ZLIB1.DLL.  If you have
+of the common DLL build of zlib, named ZLIB1.DLL.  If you have
 general questions about zlib, you should see the file "FAQ" found
 in the zlib distribution, or at the following location:
   http://www.gzip.org/zlib/zlib_faq.html
@@ -11,13 +11,9 @@ in the zlib distribution, or at the following location:
 
  1. What is ZLIB1.DLL, and how can I get it?
 
-  - ZLIB1.DLL is the official build of zlib as a DLL.
+  - ZLIB1.DLL is the common build of zlib as a DLL.
     (Please remark the character '1' in the name.)
 
-    Pointers to a precompiled ZLIB1.DLL can be found in the zlib
-    web site at:
-      http://www.zlib.net/
-
     Applications that link to ZLIB1.DLL can rely on the following
     specification:
 
@@ -379,18 +375,6 @@ in the zlib distribution, or at the following location:
     code.  But you can make your own private DLL build, under a
     different file name, as suggested in the previous answer.
 
-
-17. I made my own ZLIB1.DLL build.  Can I test it for compliance?
-
-  - We prefer that you download the official DLL from the zlib
-    web site.  If you need something peculiar from this DLL, you
-    can send your suggestion to the zlib mailing list.
-
-    However, in case you do rebuild the DLL yourself, you can run
-    it with the test programs found in the DLL distribution.
-    Running these test programs is not a guarantee of compliance,
-    but a failure can imply a detected problem.
-
 **
 
 This document is written and maintained by
diff --git a/win32/README-WIN32.txt b/win32/README-WIN32.txt
index 2790e838c..14e6398ef 100644
--- a/win32/README-WIN32.txt
+++ b/win32/README-WIN32.txt
@@ -1,6 +1,6 @@
 ZLIB DATA COMPRESSION LIBRARY
 
-zlib 1.3.0.1 is a general purpose data compression library.  All the code is
+zlib 1.3.1 is a general purpose data compression library.  All the code is
 thread safe.  The data format used by the zlib library is described by RFCs
 (Request for Comments) 1950 to 1952 in the files
 http://www.ietf.org/rfc/rfc1950.txt (zlib format), rfc1951.txt (deflate format)
@@ -16,13 +16,13 @@ is http://zlib.net/ .  Before reporting a problem, please check this site to
 verify that you have the latest version of zlib; otherwise get the latest
 version and check whether the problem still exists or not.
 
-PLEASE read DLL_FAQ.txt, and the the zlib FAQ http://zlib.net/zlib_faq.html
-before asking for help.
+PLEASE read DLL_FAQ.txt, and the zlib FAQ http://zlib.net/zlib_faq.html before
+asking for help.
 
 
 Manifest:
 
-The package zlib-1.3.0.1-win32-x86.zip will contain the following files:
+The package zlib-1.3.1-win32-x86.zip will contain the following files:
 
   README-WIN32.txt This document
   ChangeLog        Changes since previous zlib packages
diff --git a/zconf.h b/zconf.h
index fb76ffe31..62adc8d84 100644
--- a/zconf.h
+++ b/zconf.h
@@ -1,5 +1,5 @@
 /* zconf.h -- configuration of the zlib compression library
- * Copyright (C) 1995-2016 Jean-loup Gailly, Mark Adler
+ * Copyright (C) 1995-2024 Jean-loup Gailly, Mark Adler
  * For conditions of distribution and use, see copyright notice in zlib.h
  */
 
@@ -300,14 +300,6 @@
 #  endif
 #endif
 
-#ifndef Z_ARG /* function prototypes for stdarg */
-#  if defined(STDC) || defined(Z_HAVE_STDARG_H)
-#    define Z_ARG(args)  args
-#  else
-#    define Z_ARG(args)  ()
-#  endif
-#endif
-
 /* The following definitions for FAR are needed only for MSDOS mixed
  * model programming (small or medium model with some far allocations).
  * This was tested only with MSC; for other MSDOS compilers you may have
diff --git a/zconf.h.cmakein b/zconf.h.cmakein
index 310c43928..0abe3bc9d 100644
--- a/zconf.h.cmakein
+++ b/zconf.h.cmakein
@@ -1,5 +1,5 @@
 /* zconf.h -- configuration of the zlib compression library
- * Copyright (C) 1995-2016 Jean-loup Gailly, Mark Adler
+ * Copyright (C) 1995-2024 Jean-loup Gailly, Mark Adler
  * For conditions of distribution and use, see copyright notice in zlib.h
  */
 
@@ -302,14 +302,6 @@
 #  endif
 #endif
 
-#ifndef Z_ARG /* function prototypes for stdarg */
-#  if defined(STDC) || defined(Z_HAVE_STDARG_H)
-#    define Z_ARG(args)  args
-#  else
-#    define Z_ARG(args)  ()
-#  endif
-#endif
-
 /* The following definitions for FAR are needed only for MSDOS mixed
  * model programming (small or medium model with some far allocations).
  * This was tested only with MSC; for other MSDOS compilers you may have
diff --git a/zconf.h.in b/zconf.h.in
index fb76ffe31..62adc8d84 100644
--- a/zconf.h.in
+++ b/zconf.h.in
@@ -1,5 +1,5 @@
 /* zconf.h -- configuration of the zlib compression library
- * Copyright (C) 1995-2016 Jean-loup Gailly, Mark Adler
+ * Copyright (C) 1995-2024 Jean-loup Gailly, Mark Adler
  * For conditions of distribution and use, see copyright notice in zlib.h
  */
 
@@ -300,14 +300,6 @@
 #  endif
 #endif
 
-#ifndef Z_ARG /* function prototypes for stdarg */
-#  if defined(STDC) || defined(Z_HAVE_STDARG_H)
-#    define Z_ARG(args)  args
-#  else
-#    define Z_ARG(args)  ()
-#  endif
-#endif
-
 /* The following definitions for FAR are needed only for MSDOS mixed
  * model programming (small or medium model with some far allocations).
  * This was tested only with MSC; for other MSDOS compilers you may have
diff --git a/zlib.3 b/zlib.3
index ca30d078a..c716020ea 100644
--- a/zlib.3
+++ b/zlib.3
@@ -1,4 +1,4 @@
-.TH ZLIB 3 "xx Aug 2023"
+.TH ZLIB 3 "22 Jan 2024"
 .SH NAME
 zlib \- compression/decompression library
 .SH SYNOPSIS
@@ -105,9 +105,9 @@ before asking for help.
 Send questions and/or comments to zlib@gzip.org,
 or (for the Windows DLL version) to Gilles Vollant (info@winimage.com).
 .SH AUTHORS AND LICENSE
-Version 1.3.0.1
+Version 1.3.1
 .LP
-Copyright (C) 1995-2023 Jean-loup Gailly and Mark Adler
+Copyright (C) 1995-2024 Jean-loup Gailly and Mark Adler
 .LP
 This software is provided 'as-is', without any express or implied
 warranty.  In no event will the authors be held liable for any damages
diff --git a/zlib.3.pdf b/zlib.3.pdf
index da12d3718..b224532bd 100644
Binary files a/zlib.3.pdf and b/zlib.3.pdf differ
diff --git a/zlib.h b/zlib.h
index ff0fd7e8a..8d4b932ea 100644
--- a/zlib.h
+++ b/zlib.h
@@ -1,7 +1,7 @@
 /* zlib.h -- interface of the 'zlib' general purpose compression library
-  version 1.3.0.1, August xxth, 2023
+  version 1.3.1, January 22nd, 2024
 
-  Copyright (C) 1995-2023 Jean-loup Gailly and Mark Adler
+  Copyright (C) 1995-2024 Jean-loup Gailly and Mark Adler
 
   This software is provided 'as-is', without any express or implied
   warranty.  In no event will the authors be held liable for any damages
@@ -37,12 +37,12 @@
 extern "C" {
 #endif
 
-#define ZLIB_VERSION "1.3.0.1-motley"
-#define ZLIB_VERNUM 0x1301
+#define ZLIB_VERSION "1.3.1"
+#define ZLIB_VERNUM 0x1310
 #define ZLIB_VER_MAJOR 1
 #define ZLIB_VER_MINOR 3
-#define ZLIB_VER_REVISION 0
-#define ZLIB_VER_SUBREVISION 1
+#define ZLIB_VER_REVISION 1
+#define ZLIB_VER_SUBREVISION 0
 
 /*
     The 'zlib' compression library provides in-memory compression and
@@ -936,10 +936,10 @@ ZEXTERN int ZEXPORT inflateSync(z_streamp strm);
      inflateSync returns Z_OK if a possible full flush point has been found,
    Z_BUF_ERROR if no more input was provided, Z_DATA_ERROR if no flush point
    has been found, or Z_STREAM_ERROR if the stream structure was inconsistent.
-   In the success case, the application may save the current current value of
-   total_in which indicates where valid compressed data was found.  In the
-   error case, the application may repeatedly call inflateSync, providing more
-   input each time, until success or end of the input data.
+   In the success case, the application may save the current value of total_in
+   which indicates where valid compressed data was found.  In the error case,
+   the application may repeatedly call inflateSync, providing more input each
+   time, until success or end of the input data.
 */
 
 ZEXTERN int ZEXPORT inflateCopy(z_streamp dest,
@@ -1758,14 +1758,14 @@ ZEXTERN uLong ZEXPORT crc32_combine(uLong crc1, uLong crc2, z_off_t len2);
    seq1 and seq2 with lengths len1 and len2, CRC-32 check values were
    calculated for each, crc1 and crc2.  crc32_combine() returns the CRC-32
    check value of seq1 and seq2 concatenated, requiring only crc1, crc2, and
-   len2.
+   len2. len2 must be non-negative.
 */
 
 /*
 ZEXTERN uLong ZEXPORT crc32_combine_gen(z_off_t len2);
 
      Return the operator corresponding to length len2, to be used with
-   crc32_combine_op().
+   crc32_combine_op(). len2 must be non-negative.
 */
 
 ZEXTERN uLong ZEXPORT crc32_combine_op(uLong crc1, uLong crc2, uLong op);
diff --git a/zlib.map b/zlib.map
index b330b606f..31544f2e9 100644
--- a/zlib.map
+++ b/zlib.map
@@ -1,100 +1,100 @@
-ZLIB_1.2.0 {
-  global:
-    compressBound;
-    deflateBound;
-    inflateBack;
-    inflateBackEnd;
-    inflateBackInit_;
-    inflateCopy;
-  local:
-    deflate_copyright;
-    inflate_copyright;
-    inflate_fast;
-    inflate_table;
-    zcalloc;
-    zcfree;
-    z_errmsg;
-    gz_error;
-    gz_intmax;
-    _*;
-};
-
-ZLIB_1.2.0.2 {
-    gzclearerr;
-    gzungetc;
-    zlibCompileFlags;
-} ZLIB_1.2.0;
-
-ZLIB_1.2.0.8 {
-    deflatePrime;
-} ZLIB_1.2.0.2;
-
-ZLIB_1.2.2 {
-    adler32_combine;
-    crc32_combine;
-    deflateSetHeader;
-    inflateGetHeader;
-} ZLIB_1.2.0.8;
-
-ZLIB_1.2.2.3 {
-    deflateTune;
-    gzdirect;
-} ZLIB_1.2.2;
-
-ZLIB_1.2.2.4 {
-    inflatePrime;
-} ZLIB_1.2.2.3;
-
-ZLIB_1.2.3.3 {
-    adler32_combine64;
-    crc32_combine64;
-    gzopen64;
-    gzseek64;
-    gztell64;
-    inflateUndermine;
-} ZLIB_1.2.2.4;
-
-ZLIB_1.2.3.4 {
-    inflateReset2;
-    inflateMark;
-} ZLIB_1.2.3.3;
-
-ZLIB_1.2.3.5 {
-    gzbuffer;
-    gzoffset;
-    gzoffset64;
-    gzclose_r;
-    gzclose_w;
-} ZLIB_1.2.3.4;
-
-ZLIB_1.2.5.1 {
-    deflatePending;
-} ZLIB_1.2.3.5;
-
-ZLIB_1.2.5.2 {
-    deflateResetKeep;
-    gzgetc_;
-    inflateResetKeep;
-} ZLIB_1.2.5.1;
-
-ZLIB_1.2.7.1 {
-    inflateGetDictionary;
-    gzvprintf;
-} ZLIB_1.2.5.2;
-
-ZLIB_1.2.9 {
-    inflateCodesUsed;
-    inflateValidate;
-    uncompress2;
-    gzfread;
-    gzfwrite;
-    deflateGetDictionary;
-    adler32_z;
-    crc32_z;
-} ZLIB_1.2.7.1;
-
-ZLIB_1.2.12 {
-	crc32_combine_gen;
-	crc32_combine_gen64;
-	crc32_combine_op;
-} ZLIB_1.2.9;
+ZLIB_1.2.0 {
+  global:
+    compressBound;
+    deflateBound;
+    inflateBack;
+    inflateBackEnd;
+    inflateBackInit_;
+    inflateCopy;
+  local:
+    deflate_copyright;
+    inflate_copyright;
+    inflate_fast;
+    inflate_table;
+    zcalloc;
+    zcfree;
+    z_errmsg;
+    gz_error;
+    gz_intmax;
+    _*;
+};
+
+ZLIB_1.2.0.2 {
+    gzclearerr;
+    gzungetc;
+    zlibCompileFlags;
+} ZLIB_1.2.0;
+
+ZLIB_1.2.0.8 {
+    deflatePrime;
+} ZLIB_1.2.0.2;
+
+ZLIB_1.2.2 {
+    adler32_combine;
+    crc32_combine;
+    deflateSetHeader;
+    inflateGetHeader;
+} ZLIB_1.2.0.8;
+
+ZLIB_1.2.2.3 {
+    deflateTune;
+    gzdirect;
+} ZLIB_1.2.2;
+
+ZLIB_1.2.2.4 {
+    inflatePrime;
+} ZLIB_1.2.2.3;
+
+ZLIB_1.2.3.3 {
+    adler32_combine64;
+    crc32_combine64;
+    gzopen64;
+    gzseek64;
+    gztell64;
+    inflateUndermine;
+} ZLIB_1.2.2.4;
+
+ZLIB_1.2.3.4 {
+    inflateReset2;
+    inflateMark;
+} ZLIB_1.2.3.3;
+
+ZLIB_1.2.3.5 {
+    gzbuffer;
+    gzoffset;
+    gzoffset64;
+    gzclose_r;
+    gzclose_w;
+} ZLIB_1.2.3.4;
+
+ZLIB_1.2.5.1 {
+    deflatePending;
+} ZLIB_1.2.3.5;
+
+ZLIB_1.2.5.2 {
+    deflateResetKeep;
+    gzgetc_;
+    inflateResetKeep;
+} ZLIB_1.2.5.1;
+
+ZLIB_1.2.7.1 {
+    inflateGetDictionary;
+    gzvprintf;
+} ZLIB_1.2.5.2;
+
+ZLIB_1.2.9 {
+    inflateCodesUsed;
+    inflateValidate;
+    uncompress2;
+    gzfread;
+    gzfwrite;
+    deflateGetDictionary;
+    adler32_z;
+    crc32_z;
+} ZLIB_1.2.7.1;
+
+ZLIB_1.2.12 {
+	crc32_combine_gen;
+	crc32_combine_gen64;
+	crc32_combine_op;
+} ZLIB_1.2.9;
diff --git a/zutil.h b/zutil.h
index 902a304cc..48dd7feba 100644
--- a/zutil.h
+++ b/zutil.h
@@ -1,5 +1,5 @@
 /* zutil.h -- internal interface and configuration of the compression library
- * Copyright (C) 1995-2022 Jean-loup Gailly, Mark Adler
+ * Copyright (C) 1995-2024 Jean-loup Gailly, Mark Adler
  * For conditions of distribution and use, see copyright notice in zlib.h
  */
 
@@ -56,7 +56,7 @@ typedef unsigned long  ulg;
 extern z_const char * const z_errmsg[10]; /* indexed by 2-zlib_error */
 /* (size given to avoid silly warnings with Visual C++) */
 
-#define ERR_MSG(err) z_errmsg[Z_NEED_DICT-(err)]
+#define ERR_MSG(err) z_errmsg[(err) < -6 || (err) > 2 ? 9 : 2 - (err)]
 
 #define ERR_RETURN(strm,err) \
   return (strm->msg = ERR_MSG(err), (err))
@@ -137,17 +137,8 @@ extern z_const char * const z_errmsg[10]; /* indexed by 2-zlib_error */
 #  endif
 #endif
 
-#if defined(MACOS) || defined(TARGET_OS_MAC)
+#if defined(MACOS)
 #  define OS_CODE  7
-#  ifndef Z_SOLO
-#    if defined(__MWERKS__) && __dest_os != __be_os && __dest_os != __win32_os
-#      include <unix.h> /* for fdopen */
-#    else
-#      ifndef fdopen
-#        define fdopen(fd,mode) NULL /* No fdopen() */
-#      endif
-#    endif
-#  endif
 #endif
 
 #ifdef __acorn
@@ -170,18 +161,6 @@ extern z_const char * const z_errmsg[10]; /* indexed by 2-zlib_error */
 #  define OS_CODE 19
 #endif
 
-#if defined(_BEOS_) || defined(RISCOS)
-#  define fdopen(fd,mode) NULL /* No fdopen() */
-#endif
-
-#if (defined(_MSC_VER) && (_MSC_VER > 600)) && !defined __INTERIX
-#  if defined(_WIN32_WCE)
-#    define fdopen(fd,mode) NULL /* No fdopen() */
-#  else
-#    define fdopen(fd,type)  _fdopen(fd,type)
-#  endif
-#endif
-
 #if defined(__BORLANDC__) && !defined(MSDOS)
   #pragma warn -8004
   #pragma warn -8008