diff --git a/assets/js/app.js b/assets/js/app.js
index f65de2e..118e3b5 100644
--- a/assets/js/app.js
+++ b/assets/js/app.js
@@ -277,3 +277,14 @@ return `
     </div>
 `
 }
+
+// Check if local CRDT consistent with server CRDT
+var check_btn = document.getElementById("check_btn");
+check_btn.onclick = function() {
+    channel.push("check", {
+        value: crdt.toString()
+    }).receive("ok", resp => {
+        console.log(`Response: ${resp["flag"]}`)
+    })
+}
+
diff --git a/lib/codeshare/application.ex b/lib/codeshare/application.ex
index 96f842a..f305107 100644
--- a/lib/codeshare/application.ex
+++ b/lib/codeshare/application.ex
@@ -14,7 +14,10 @@ defmodule Codeshare.Application do
       CodeshareWeb.Endpoint,
       # Starts a worker by calling: Codeshare.Worker.start_link(arg)
       # {Codeshare.Worker, arg},
-      CodeshareWeb.Presence
+      # Start Presence
+      CodeshareWeb.Presence,
+      # Start CRDT Supervisor
+      Codeshare.CRDT.Supervisor
     ]
 
     # See https://hexdocs.pm/elixir/Supervisor.html
diff --git a/lib/codeshare/crdt/character.ex b/lib/codeshare/crdt/character.ex
new file mode 100644
index 0000000..e744e6b
--- /dev/null
+++ b/lib/codeshare/crdt/character.ex
@@ -0,0 +1,170 @@
+defmodule Codeshare.Identifier do
+  @moduledoc """
+  List of identifiers define the 'position'
+  of a character in CRDT
+  """
+  alias __MODULE__
+
+  defstruct [
+    position: 0,
+    siteID: -1
+  ]
+
+  @doc """
+  Helper to convert payload from channel
+  to struct
+  """
+  def to_struct(identifier_map) do
+    map = identifier_map
+    %Identifier{
+      position: map["position"],
+      siteID: map["siteID"]
+    }
+  end
+
+  @doc """
+  Convert to string representation
+  """
+  def to_string(identifier) do
+    # Client and server have diff infinity values!
+    if identifier.siteID == 16777216 do
+      "[#{identifier.position}, Infinity]"
+    else
+      "[#{identifier.position}, #{identifier.siteID}]"
+    end
+  end
+
+  @doc """
+  Check if two identifiers are equal
+  """
+  def is_equal(id1, id2) do
+    id1.position == id2.position && id1.siteID == id2.siteID
+  end
+
+  @doc """
+  is `id1` > `id2` ? [Identifiers]
+  """
+  def is_greater(id1, id2) do
+    if id1.position == id2.position do
+      id1.siteID > id2.siteID
+    else
+      id1.position > id2.position
+    end
+  end
+
+  # TODO: Add struct validation?
+end
+
+defmodule Codeshare.Character do
+  @moduledoc """
+  Represensts each 'character' in
+  the CRDT text
+  """
+  alias __MODULE__
+  alias Codeshare.Identifier
+
+  defstruct [
+    ch: "",
+    identifiers: [%Identifier{}]
+  ]
+
+  @doc """
+  Helper to convert payload from channel
+  to struct
+  """
+  def to_struct(character_map) do
+    map = character_map
+    %Character{
+      ch: map["ch"],
+      identifiers: to_identifiers_struct_list(map["identifiers"])
+    }
+  end
+
+  @doc """
+  Convert to string representation
+  """
+  def to_string(character) do
+    "{#{character.ch}: [#{to_string_id_list(character.identifiers)}]}"
+  end
+
+  @doc """
+  Check if two characters are equal
+  """
+  def is_equal(character1, character2) do
+    if character1.ch != character2.ch || 
+        length(character1.identifiers) != length(character2.identifiers) do
+      false      
+    else
+      is_identifier_list_equal(character1.identifiers, 
+        character2.identifiers)
+    end
+  end
+
+  @doc """
+  is `character1` > `character2` ?
+  """
+  def is_greater(character1, character2) do
+    is_identifier_list_greater(character1.identifiers, 
+                                character2.identifiers)
+  end
+
+  # Helper functions
+
+  defp to_identifiers_struct_list(identifiers_map_list) do
+    if identifiers_map_list == [] do
+      []
+    else
+      [h | t] = identifiers_map_list
+      [Identifier.to_struct(h) | to_identifiers_struct_list(t)]
+    end
+  end 
+
+  defp is_identifier_list_equal(id_list1, id_list2) do
+    if id_list1 == [] && id_list2 == [] do
+      true
+    else
+      [id1 | id_list1] = id_list1
+      [id2 | id_list2] = id_list2
+
+      if Identifier.is_equal(id1, id2) do
+        is_identifier_list_equal(id_list1, id_list2)
+      else
+        false
+      end
+    end
+  end
+
+  defp is_identifier_list_greater(id_list1, id_list2) do
+
+    cond do
+      id_list1 == [] ->
+        false
+      id_list2 == [] ->
+        true
+      true ->
+        [id1 | id_list1] = id_list1
+        [id2 | id_list2] = id_list2
+
+        cond do
+          Identifier.is_greater(id1, id2) ->
+            true
+          Identifier.is_greater(id2, id1) ->
+            false
+          Identifier.is_equal(id1, id2) ->
+            is_identifier_list_greater(id_list1, id_list2)
+        end
+    end
+
+  end
+
+  defp to_string_id_list(id_list) do
+    [first_id | id_list] = id_list
+    if id_list == [] do
+      "#{Identifier.to_string(first_id)}"
+    else
+      "#{Identifier.to_string(first_id)}, #{to_string_id_list(id_list)}"
+    end
+  end
+
+  # TODO: Add struct validation?
+end
\ No newline at end of file
diff --git a/lib/codeshare/crdt/crdt.ex b/lib/codeshare/crdt/crdt.ex
new file mode 100644
index 0000000..c2b85fa
--- /dev/null
+++ b/lib/codeshare/crdt/crdt.ex
@@ -0,0 +1,196 @@
+defmodule Codeshare.CRDT do
+  @moduledoc """
+  Manages the server-side CRDT
+  """
+  use Agent
+  alias Codeshare.{Character, Identifier}
+
+  # [] arg required by supervisor
+  def start_link(_opts) do
+    fn -> [[
+      %Character{
+        ch: "",
+        identifiers: [%Identifier{
+          position: 0,
+          siteID: -1
+        }]
+      },
+      %Character{
+        ch: "",
+        identifiers: [%Identifier{
+            position: 1,
+            siteID: 16777216 #TODO: Infinity for now; think of something
+          }]
+      }
+    ]]
+    end |> Agent.start_link()
+    # TODO: Registered with module name, which doesn't allow server crdt per session
+    # (It allows for only one server crdt process)
+    # Need another process to map session id with corresponding server crdt pid
+  end
+
+  @doc """
+  Put payload data recived from channel
+  into CRDT
+  """
+  def put(crdt, payload) do
+    character = Character.to_struct(payload["character"])
+    case Map.get(payload, "type") do
+      "input" -> 
+        remote_insert(crdt, character)
+      "delete" ->
+        remote_delete(crdt, character)
+      "inputnewline" ->
+        remote_insert_newline(crdt, character)
+      "deletenewline" ->
+        remote_delete_newline(crdt, character)
+    end
+  end
+
+  @doc """
+  Get CRDT data
+  """
+  def get(crdt) do
+    Agent.get(crdt, & &1)
+  end
+
+  @doc """
+  Get CRDT string representation
+  """
+  def get_string(crdt) do
+    Agent.get(crdt, & convert_to_string(&1))
+  end
+
+  def stop(crdt) do
+    Agent.stop(crdt)
+  end
+
+  # Helper functions
+
+  defp remote_insert(crdt, character) do
+    Agent.update(crdt, fn crdt -> insert_character(crdt, character) end)
+  end
+
+  defp remote_delete(crdt, character) do
+    Agent.update(crdt, fn crdt -> delete_character(crdt, character) end)
+  end
+
+  defp remote_insert_newline(crdt, character) do
+    Agent.update(crdt, fn crdt -> insert_newline(crdt, character) end)
+  end
+
+  defp remote_delete_newline(crdt, character) do
+    Agent.update(crdt, fn crdt -> delete_newline(crdt, character) end)
+  end
+
+  defp insert_character(crdt, character) do
+    
+    [first_line | crdt] = crdt
+    last_ch = List.last(first_line) # NOTE: Takes linear time :(
+
+    if Character.is_greater(last_ch, character) do
+      [insert_character_on_line(first_line, character) | crdt]
+    else
+      [first_line | insert_character(crdt, character)]
+    end
+  end
+
+  defp insert_character_on_line(line, character) do
+
+    [first_ch | line] = line
+
+    if Character.is_greater(first_ch, character) do
+      [character | [ first_ch | line] ]
+    else
+      [first_ch | insert_character_on_line(line, character)]
+    end
+  end
+
+  defp delete_character(crdt, character) do
+    
+    [first_line | crdt] = crdt
+    last_ch = List.last(first_line) # NOTE: Takes linear time :(
+
+    if Character.is_greater(last_ch, character) do
+      [delete_character_on_line(first_line, character) | crdt]
+    else
+      [first_line | delete_character(crdt, character)]
+    end
+  end
+
+  defp delete_character_on_line(line, character) do
+
+    [first_ch | line] = line
+
+    if Character.is_equal(first_ch, character) do
+      line
+    else
+      [first_ch | delete_character_on_line(line, character)]
+    end
+  end
+
+  defp insert_newline(crdt, character) do
+    
+    [first_line | crdt] = crdt
+    last_ch = List.last(first_line) # NOTE: Takes linear time :(
+
+    if Character.is_greater(last_ch, character) do
+      insert_newline_on_line(first_line, character) ++ crdt
+    else
+      [first_line | insert_newline(crdt, character)]
+    end
+  end
+
+  defp insert_newline_on_line(line, character) do
+    
+    [first_ch | line] = line
+
+    if Character.is_greater(first_ch, character) do
+      delimeter_ch = %Character{
+        ch: "",
+        identifiers: character.identifiers
+      }
+      line1 = [delimeter_ch]
+      line2 = [delimeter_ch | [first_ch | line] ]
+      [line1, line2]
+    else
+      lines = insert_newline_on_line(line, character)
+      [line1 | [line2]] = lines
+      line1 = [first_ch | line1]
+      [line1 | [line2]]
+    end
+  end
+
+  defp delete_newline(crdt, character) do
+    
+    [first_line | crdt] = crdt
+    last_ch = List.last(first_line) # NOTE: Takes linear time :(
+
+    if Character.is_equal(last_ch, character) do
+      line1 = first_line |> Enum.reverse |> tl |> Enum.reverse
+      [[_ | line2] | crdt] = crdt
+      [line1++line2 | crdt]
+    else
+      [first_line | delete_newline(crdt, character)]
+    end
+  end
+
+  defp convert_to_string(crdt) do
+    if crdt == [] do
+      ""
+    else
+      [first_line | crdt] = crdt
+      "#{convert_line_to_string(first_line)}\n#{convert_to_string(crdt)}"
+    end
+  end
+
+  defp convert_line_to_string(line) do
+    [first_ch | line] = line
+    if line == [] do
+      "#{Character.to_string(first_ch)}"
+    else
+      "#{Character.to_string(first_ch)}, #{convert_line_to_string(line)}"
+    end
+  end
+
+end
\ No newline at end of file
diff --git a/lib/codeshare/crdt/registry.ex b/lib/codeshare/crdt/registry.ex
new file mode 100644
index 0000000..03ec107
--- /dev/null
+++ b/lib/codeshare/crdt/registry.ex
@@ -0,0 +1,97 @@
+defmodule Codeshare.CRDT.Registry do
+  @moduledoc """
+  Registry mapping session id -> crdt process
+  """
+  alias __MODULE__
+  use GenServer
+  alias Codeshare.CRDT
+
+  ## API to accessing CRDT
+
+  @doc """
+  Start the registry
+  """
+  def start_link(opts) do
+    GenServer.start_link(__MODULE__, :ok, opts)
+  end
+
+  def create(server, session_id) do
+    GenServer.cast(server, {:create, session_id})
+  end
+
+  def put(server, session_id, payload) do
+    GenServer.cast(server, {:put, session_id, payload})
+  end
+
+  def stop(server, session_id) do
+    GenServer.cast(server, {:stop, session_id})
+  end
+
+  def get_string(server, session_id) do
+    GenServer.call(server, {:get_string, session_id})
+  end
+
+  # Debugging function
+  def get_sessions(server) do
+    GenServer.call(server, {:get_sessions})
+  end
+
+  ## Defining GenSever Callback
+
+  @impl true
+  def init(:ok) do
+    sessions = %{}
+    refs = %{}
+    {:ok, {sessions, refs}}
+  end
+
+  @impl true
+  def handle_cast({:create, session_id}, {sessions, refs}) do
+    if Map.has_key?(sessions, session_id) do
+      {:noreply, {sessions, refs}}
+    else
+      {:ok, crdt} = CRDT.start_link([])
+      ref = Process.monitor(crdt)
+      refs = Map.put(refs, ref, session_id)
+      sessions = Map.put(sessions, session_id, crdt)
+      {:noreply, {sessions, refs}}
+    end
+  end
+
+  @impl true
+  def handle_cast({:put, session_id, payload}, {sessions, refs}) do
+    {:ok, crdt} = Map.fetch(sessions, session_id)
+    CRDT.put(crdt, payload)
+    {:noreply, {sessions, refs}}
+  end
+
+  @impl true
+  def handle_cast({:stop, session_id}, {sessions, refs}) do
+    {:ok, crdt} = Map.fetch(sessions, session_id)
+    CRDT.stop(crdt)
+    {:noreply, {sessions, refs}}
+  end
+
+  @impl true
+  def handle_call({:get_string, session_id}, _from, {sessions, refs}) do
+    {:ok, crdt} = Map.fetch(sessions, session_id)
+    {:reply, CRDT.get_string(crdt), {sessions, refs}}
+  end
+
+  @impl true
+  def handle_call({:get_sessions}, _from, {sessions, refs}) do
+    {:reply, sessions, {sessions, refs}}
+  end
+
+  @impl true
+  def handle_info({:DOWN, ref, :process, _pid, _reason}, {sessions, refs}) do
+    {session_id, refs} = Map.pop(refs, ref)
+    sessions = Map.delete(sessions, session_id)
+    {:noreply, {sessions, refs}}
+  end
+
+  @impl true
+  def handle_info(_msg, state) do
+    {:noreply, state}
+  end
+end
\ No newline at end of file
diff --git a/lib/codeshare/crdt/supervisor.ex b/lib/codeshare/crdt/supervisor.ex
new file mode 100644
index 0000000..9ef89d9
--- /dev/null
+++ b/lib/codeshare/crdt/supervisor.ex
@@ -0,0 +1,22 @@
+defmodule Codeshare.CRDT.Supervisor do
+  @moduledoc """
+  Supervise CRDT Registry
+  and CRDT processes
+  """
+  use Supervisor
+  alias Codeshare.CRDT
+
+  def start_link(opts) do
+    Supervisor.start_link(__MODULE__, :ok, opts)
+  end
+
+  @impl true
+  def init(:ok) do
+    children = [
+      {CRDT.Registry, name: CRDT.Registry}
+    ]
+
+    Supervisor.init(children, strategy: :one_for_one)
+  end
+
+end
\ No newline at end of file
diff --git a/lib/codeshare_web/channels/room_channel.ex b/lib/codeshare_web/channels/room_channel.ex
index 961cb2c..7c22366 100644
--- a/lib/codeshare_web/channels/room_channel.ex
+++ b/lib/codeshare_web/channels/room_channel.ex
@@ -2,9 +2,18 @@ defmodule CodeshareWeb.RoomChannel do
   use CodeshareWeb, :channel
   import Ecto.Query, only: [from: 2]
   alias CodeshareWeb.Presence
+  alias Codeshare.CRDT
 
   def join("room:" <> room_id, payload, socket) do
     if authorized?(payload) do
+      # Add CRDT process
+      CRDT.Registry.create(CRDT.Registry, room_id)
+
+      # Print active sessions
+      sessions = CRDT.Registry.get_sessions(CRDT.Registry)
+      IO.puts "Active sessions"
+      IO.inspect sessions
+      
       query = from entry in "editor_state",
             select: entry.data,
             where: entry.room_id == ^(room_id)
@@ -44,6 +53,11 @@ defmodule CodeshareWeb.RoomChannel do
   # It is also common to receive messages from the client and
   # broadcast to everyone in the current topic (room:lobby).
   def handle_in("shout", payload, socket) do
+
+    # Update server-side CRDT
+    CRDT.Registry.put(CRDT.Registry, socket.assigns.room_id, payload)
+    # IO.inspect CRDT.get()
+
     editor = %Codeshare.Editor{}
     changeset = Codeshare.Editor.changeset(editor, %{data: payload, room_id: socket.assigns.room_id})
     Codeshare.Repo.insert(changeset)
@@ -57,6 +71,19 @@ defmodule CodeshareWeb.RoomChannel do
     {:noreply, socket}
   end
 
+  def handle_in("check", payload, socket) do
+    IO.puts "CRDT: #{socket.assigns.user_id}:"
+    IO.puts payload["value"]
+    IO.puts "CRDT: Server:"
+    IO.puts CRDT.Registry.get_string(CRDT.Registry, socket.assigns.room_id)
+
+    if payload["value"] == CRDT.Registry.get_string(CRDT.Registry, socket.assigns.room_id) do
+      {:reply, {:ok, %{"flag" => true}}, socket}
+    else
+      {:reply, {:ok, %{"flag" => false}}, socket}
+    end
+  end
+
   def terminate(_ , socket) do
     # When last active channel is terminating, 
     # empty the database
@@ -64,6 +91,10 @@ defmodule CodeshareWeb.RoomChannel do
       query = from editor in "editor_state",
             select: editor.data
       Codeshare.Repo.delete_all(query)
+
+      # Stop CRDT process
+      CRDT.Registry.stop(CRDT.Registry, socket.assigns.room_id)
+      IO.puts "Session #{String.slice(socket.assigns.room_id, 0..6)} terminated"
     end
     :ok
   end
diff --git a/lib/codeshare_web/templates/page/index.html.eex b/lib/codeshare_web/templates/page/index.html.eex
index 7fa74ff..07ea8cc 100644
--- a/lib/codeshare_web/templates/page/index.html.eex
+++ b/lib/codeshare_web/templates/page/index.html.eex
@@ -45,7 +45,7 @@ function updateMode() {
 </script>
 
 <button id="compile_btn">Compile</button>
-
+<button id="check_btn">Check</button>
 Current user: <span id="my_id" style="font-weight:bold"></span>
 <div class="col-md-3">
   <div class="card">