diff --git a/config/config.exs b/config/config.exs
index 9656d8e51a..77a4e046c6 100644
--- a/config/config.exs
+++ b/config/config.exs
@@ -5,7 +5,8 @@ config :logger, :console,
   format: "\n$time $metadata[$level] $message\n"
 
 config :phoenix,
-  json_library: Jason,
+  # TODO: Remove the `json_library` check once `JSON` becomes the standard `Phoenix.json_library/1`
+  json_library: (if Code.ensure_loaded?(JSON), do: JSON, else: Jason),
   stacktrace_depth: 20,
   trim_on_html_eex_engine: false
 
diff --git a/guides/controllers.md b/guides/controllers.md
index 572f4407af..40ae3abdbe 100644
--- a/guides/controllers.md
+++ b/guides/controllers.md
@@ -94,7 +94,7 @@ end
 
 Now [`/hello/Frank`] in your browser should display `From messenger Frank` as plain text without any HTML.
 
-A step beyond this is rendering pure JSON with the [`json/2`] function. We need to pass it something that the [Jason library](`Jason`) can decode into JSON, such as a map. (Jason is one of Phoenix's dependencies.)
+A step beyond this is rendering pure JSON with the [`json/2`] function. We need to pass it something that the [JSON library](https://hexdocs.pm/elixir/JSON.html) can decode into JSON, such as a map.
 
 ```elixir
 def show(conn, %{"messenger" => messenger}) do
diff --git a/guides/json_and_apis.md b/guides/json_and_apis.md
index e2705c9a3e..7e1683fc6c 100644
--- a/guides/json_and_apis.md
+++ b/guides/json_and_apis.md
@@ -171,7 +171,7 @@ defmodule HelloWeb.UrlJSON do
 end
 ```
 
-This view is very simple. The `index` function receives all URLs, and converts them into a list of maps. Those maps are placed inside the data key at the root, exactly as we saw when interfacing with our application from `cURL`. In other words, our JSON view converts our complex data into simple Elixir data-structures. Once our view layer returns, Phoenix uses the `Jason` library to encode JSON and send the response to the client.
+This view is very simple. The `index` function receives all URLs, and converts them into a list of maps. Those maps are placed inside the data key at the root, exactly as we saw when interfacing with our application from `cURL`. In other words, our JSON view converts our complex data into simple Elixir data-structures. Once our view layer returns, Phoenix uses the built-in [JSON library](https://hexdocs.pm/elixir/1.18/JSON.html) to encode JSON and send the response to the client.
 
 If you explore the remaining controller, you will learn the `show` action is similar to the `index` one. For `create`, `update`, and `delete` actions, Phoenix uses one other important feature, called "Action fallback".
 
diff --git a/guides/plug.md b/guides/plug.md
index 308a60b877..36c2766f2e 100644
--- a/guides/plug.md
+++ b/guides/plug.md
@@ -153,7 +153,7 @@ The default endpoint plugs do quite a lot of work. Here they are in order:
 
 - `Plug.Telemetry` - adds instrumentation points so Phoenix can log the request path, status code and request time by default.
 
-- `Plug.Parsers` - parses the request body when a known parser is available. By default, this plug can handle URL-encoded, multipart and JSON content (with `Jason`). The request body is left untouched if the request content-type cannot be parsed.
+- `Plug.Parsers` - parses the request body when a known parser is available. By default, this plug can handle URL-encoded, multipart and JSON content. The request body is left untouched if the request content-type cannot be parsed.
 
 - `Plug.MethodOverride` - converts the request method to PUT, PATCH or DELETE for POST requests with a valid `_method` parameter.
 
diff --git a/installer/templates/phx_single/config/config.exs b/installer/templates/phx_single/config/config.exs
index 11496cdbc4..a15fcba6f3 100644
--- a/installer/templates/phx_single/config/config.exs
+++ b/installer/templates/phx_single/config/config.exs
@@ -59,8 +59,8 @@ config :logger, :default_formatter,
   format: "$time $metadata[$level] $message\n",
   metadata: [:request_id]
 
-# Use Jason for JSON parsing in Phoenix
-config :phoenix, :json_library, Jason
+# Use built-in `JSON` for JSON parsing in Phoenix
+config :phoenix, :json_library, JSON
 
 # Import environment specific config. This must remain at the bottom
 # of this file so it overrides the configuration defined above.
diff --git a/installer/templates/phx_umbrella/config/extra_config.exs b/installer/templates/phx_umbrella/config/extra_config.exs
index 713d9b6bc4..9af3ece5fa 100644
--- a/installer/templates/phx_umbrella/config/extra_config.exs
+++ b/installer/templates/phx_umbrella/config/extra_config.exs
@@ -5,8 +5,8 @@ config :logger, :default_formatter,
   format: "$time $metadata[$level] $message\n",
   metadata: [:request_id]
 
-# Use Jason for JSON parsing in Phoenix
-config :phoenix, :json_library, Jason
+# Use built-in `JSON` for JSON parsing in Phoenix
+config :phoenix, :json_library, JSON
 
 # Import environment specific config. This must remain at the bottom
 # of this file so it overrides the configuration defined above.
diff --git a/installer/test/phx_new_test.exs b/installer/test/phx_new_test.exs
index c1c1166f62..f97068a17c 100644
--- a/installer/test/phx_new_test.exs
+++ b/installer/test/phx_new_test.exs
@@ -54,7 +54,7 @@ defmodule Mix.Tasks.Phx.NewTest do
       assert_file("phx_blog/config/config.exs", fn file ->
         assert file =~ "ecto_repos: [PhxBlog.Repo]"
         assert file =~ "generators: [timestamp_type: :utc_datetime]"
-        assert file =~ "config :phoenix, :json_library, Jason"
+        assert file =~ "config :phoenix, :json_library, JSON"
         assert file =~ ~s[cd: Path.expand("../assets", __DIR__),]
         refute file =~ "namespace: PhxBlog"
         refute file =~ "config :phx_blog, :generators"
diff --git a/installer/test/phx_new_umbrella_test.exs b/installer/test/phx_new_umbrella_test.exs
index 61258f8cbe..aaa8cbb70d 100644
--- a/installer/test/phx_new_umbrella_test.exs
+++ b/installer/test/phx_new_umbrella_test.exs
@@ -63,7 +63,7 @@ defmodule Mix.Tasks.Phx.New.UmbrellaTest do
         assert file =~ ~r/config :esbuild/
         assert file =~ "cd: Path.expand(\"../apps/phx_umb_web/assets\", __DIR__)"
         assert file =~ ~S[import_config "#{config_env()}.exs"]
-        assert file =~ "config :phoenix, :json_library, Jason"
+        assert file =~ "config :phoenix, :json_library, JSON"
         assert file =~ "ecto_repos: [PhxUmb.Repo]"
         assert file =~ ":phx_umb_web, PhxUmbWeb.Endpoint"
         assert file =~ "generators: [context_app: :phx_umb]\n"
diff --git a/integration_test/config/config.exs b/integration_test/config/config.exs
index a596f1c7d3..308398d6cc 100644
--- a/integration_test/config/config.exs
+++ b/integration_test/config/config.exs
@@ -1,6 +1,7 @@
 import Config
 
-config :phoenix, :json_library, Jason
+# TODO: Remove the `json_library` check once `JSON` becomes the standard `Phoenix.json_library/1`
+config :phoenix, :json_library, (if Code.ensure_loaded?(JSON), do: JSON, else: Jason)
 
 config :swoosh, api_client: false
 
diff --git a/lib/phoenix.ex b/lib/phoenix.ex
index 9a4d5b7ac3..0d484dc898 100644
--- a/lib/phoenix.ex
+++ b/lib/phoenix.ex
@@ -45,6 +45,7 @@ defmodule Phoenix do
 
   """
   def json_library do
+    # TODO: Change the default json library to JSON in Phoenix v2.0
     Application.get_env(:phoenix, :json_library, Jason)
   end
 
diff --git a/test/phoenix/socket/v1_json_serializer_test.exs b/test/phoenix/socket/v1_json_serializer_test.exs
index 62652d3f26..0bfb7f4881 100644
--- a/test/phoenix/socket/v1_json_serializer_test.exs
+++ b/test/phoenix/socket/v1_json_serializer_test.exs
@@ -24,7 +24,7 @@ defmodule Phoenix.Socket.V1.JSONSerializerTest do
     msg = %Message{topic: "t", event: "e", payload: "m"}
     encoded = encode!(@serializer, msg)
 
-    assert Jason.decode!(encoded) == %{
+    assert Phoenix.json_library().decode!(encoded) == %{
              "event" => "e",
              "payload" => "m",
              "ref" => nil,
@@ -36,7 +36,7 @@ defmodule Phoenix.Socket.V1.JSONSerializerTest do
     msg = %Reply{topic: "t", ref: "null"}
     encoded = encode!(@serializer, msg)
 
-    assert Jason.decode!(encoded) == %{
+    assert Phoenix.json_library().decode!(encoded) == %{
              "event" => "phx_reply",
              "payload" => %{"response" => nil, "status" => nil},
              "ref" => "null",
@@ -61,7 +61,7 @@ defmodule Phoenix.Socket.V1.JSONSerializerTest do
     msg = %Broadcast{topic: "t", event: "e", payload: "m"}
     encoded = fastlane!(@serializer, msg)
 
-    assert Jason.decode!(encoded) == %{
+    assert Phoenix.json_library().decode!(encoded) == %{
              "event" => "e",
              "payload" => "m",
              "ref" => nil,
diff --git a/test/phoenix/socket/v2_json_serializer_test.exs b/test/phoenix/socket/v2_json_serializer_test.exs
index c534ff47d3..acfb2ef7e9 100644
--- a/test/phoenix/socket/v2_json_serializer_test.exs
+++ b/test/phoenix/socket/v2_json_serializer_test.exs
@@ -102,7 +102,7 @@ defmodule Phoenix.Socket.V2.JSONSerializerTest do
     msg = %Reply{topic: "t", payload: %{m: 1}}
     encoded = encode!(@serializer, msg)
 
-    assert Jason.decode!(encoded) == [
+    assert Phoenix.json_library().decode!(encoded) == [
              nil,
              nil,
              "t",
diff --git a/test/phoenix/test/conn_test.exs b/test/phoenix/test/conn_test.exs
index 724de7a040..ffadd98065 100644
--- a/test/phoenix/test/conn_test.exs
+++ b/test/phoenix/test/conn_test.exs
@@ -328,13 +328,19 @@ defmodule Phoenix.Test.ConnTest do
       build_conn(:get, "/") |> resp(200, "ok") |> json_response(200)
     end
 
-    assert_raise Jason.DecodeError,
-                 "unexpected byte at position 0: 0x6F (\"o\")", fn ->
+    json_error =
+      case Phoenix.json_library() do
+        JSON -> JSON.DecodeError
+        Jason -> Jason.DecodeError
+      end
+
+    assert_raise json_error,
+                 ~r/invalid byte 111 at position \(byte offset\) 0|unexpected byte at position 0: 0x6F \("o"\)/, fn ->
       build_conn(:get, "/") |> put_resp_content_type("application/json")
                       |> resp(200, "ok") |> json_response(200)
     end
 
-    assert_raise Jason.DecodeError, ~r/unexpected end of input at position 0/, fn ->
+    assert_raise json_error, ~r/unexpected end of JSON binary at position \(byte offset\) 0|unexpected end of input at position 0/, fn ->
       build_conn(:get, "/")
       |> put_resp_content_type("application/json")
       |> resp(200, "")