diff --git a/src/main/java/pt/ua/deti/codespell/codespellbackend/exception/implementations/InvalidEmailException.java b/src/main/java/pt/ua/deti/codespell/codespellbackend/exception/implementations/InvalidEmailException.java
new file mode 100644
index 0000000..55c95d7
--- /dev/null
+++ b/src/main/java/pt/ua/deti/codespell/codespellbackend/exception/implementations/InvalidEmailException.java
@@ -0,0 +1,7 @@
+package pt.ua.deti.codespell.codespellbackend.exception.implementations;
+
+public class InvalidEmailException extends RuntimeException{
+    public InvalidEmailException(String message) {
+        super(message);
+    }
+}
diff --git a/src/main/java/pt/ua/deti/codespell/codespellbackend/exception/implementations/InvalidPasswordException.java b/src/main/java/pt/ua/deti/codespell/codespellbackend/exception/implementations/InvalidPasswordException.java
new file mode 100644
index 0000000..8769ad8
--- /dev/null
+++ b/src/main/java/pt/ua/deti/codespell/codespellbackend/exception/implementations/InvalidPasswordException.java
@@ -0,0 +1,7 @@
+package pt.ua.deti.codespell.codespellbackend.exception.implementations;
+
+public class InvalidPasswordException extends RuntimeException{
+    public InvalidPasswordException(String message) {
+        super(message);
+    }
+}
diff --git a/src/main/java/pt/ua/deti/codespell/codespellbackend/exception/implementations/InvalidUsernameException.java b/src/main/java/pt/ua/deti/codespell/codespellbackend/exception/implementations/InvalidUsernameException.java
new file mode 100644
index 0000000..efe6d5c
--- /dev/null
+++ b/src/main/java/pt/ua/deti/codespell/codespellbackend/exception/implementations/InvalidUsernameException.java
@@ -0,0 +1,7 @@
+package pt.ua.deti.codespell.codespellbackend.exception.implementations;
+
+public class InvalidUsernameException extends RuntimeException{
+    public InvalidUsernameException(String message) {
+        super(message);
+    }
+}
diff --git a/src/main/java/pt/ua/deti/codespell/codespellbackend/service/UserService.java b/src/main/java/pt/ua/deti/codespell/codespellbackend/service/UserService.java
index 13dd336..d51c752 100644
--- a/src/main/java/pt/ua/deti/codespell/codespellbackend/service/UserService.java
+++ b/src/main/java/pt/ua/deti/codespell/codespellbackend/service/UserService.java
@@ -1,9 +1,14 @@
 package pt.ua.deti.codespell.codespellbackend.service;
 
+import java.util.regex.Pattern;
+
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.lang.NonNull;
 import org.springframework.stereotype.Service;
 import pt.ua.deti.codespell.codespellbackend.exception.implementations.ExistentUserException;
+import pt.ua.deti.codespell.codespellbackend.exception.implementations.InvalidEmailException;
+import pt.ua.deti.codespell.codespellbackend.exception.implementations.InvalidPasswordException;
+import pt.ua.deti.codespell.codespellbackend.exception.implementations.InvalidUsernameException;
 import pt.ua.deti.codespell.codespellbackend.exception.implementations.UserNotFoundException;
 import pt.ua.deti.codespell.codespellbackend.model.User;
 import pt.ua.deti.codespell.codespellbackend.repository.UserRepository;
@@ -37,11 +42,28 @@ public User findByEmail(String email) {
     }
 
     public void registerUser(User user) {
+        String emailRegex = "^[\\w!#$%&'*+/=?`{|}~^-]+(?:\\.[\\w!#$%&'*+/=?`{|}~^-]+)*@(?:[a-zA-Z0-9-]+\\.)+[a-zA-Z]{2,6}$";
+        boolean emailChecker = Pattern.matches(emailRegex, user.getEmail());
 
         if (userRepository.existsByUsername(user.getUsername()))
             throw new ExistentUserException("The provided username is already taken.");
+        else if (userRepository.existsByEmail(user.getEmail()))
+            throw new ExistentUserException("The provided email is already taken.");
+        else if (!emailChecker)
+            throw new InvalidEmailException("The provided email is invalid.");
+        else if (user.getPassword().length() < 6 || user.getPassword() == null)
+            throw new InvalidPasswordException("The provided password is invalid.");
+        else if (user.getUsername().length() < 3 || user.getUsername() == null)
+            throw new InvalidUsernameException("The provided username is invalid.");
         userRepository.save(user);
 
     }
 
+    public void updateUser(User user) {
+        
+        if (!userRepository.existsByUsername(user.getUsername()))
+            throw new UserNotFoundException(String.format("The user %s could not be found.", user.getUsername()));
+        userRepository.save(user);
+
+    }
 }