HTTP 510 Not Extended


The HTTP 510 Not Extended status code is a non-standard status code that indicates further extensions to the request are required for the server to fulfill it.


The HTTP 510 response is used to inform the client that the server requires additional extensions to the request in order to proceed.


Client Behavior:

  1. Send Request: The client sends a request that lacks the required extensions.
  2. Receive Response: The client receives an HTTP 510 status code indicating that further extensions are needed.

Server Behavior:

  1. Missing Extensions: The server identifies that the client’s request lacks the required extensions.
  2. Send Response: The server sends a 510 Not Extended response to the client.


  • Protocol Extensions: Used in scenarios where the server requires additional protocol extensions from the client.

Sequence Diagram

Illustrating the process for an HTTP 510 response:

    participant Client
    participant Server

    Note over Client: Step 1: Client sends a request without required extensions
    Client->>Server: GET /resource HTTP/1.1 (Step 1)

    Note over Server: Step 2: Server detects missing extensions
    Server-->>Client: HTTP/1.1 510 Not Extended (Step 2)

Curl Request and Response Example

Sending a request using Curl without the required extensions:

curl -i
# Expected response: HTTP/1.1 510 Not Extended

PHP cURL Request and Response Example

PHP script using cURL to handle a 510 Not Extended response:

$ch = curl_init('');
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
$response = curl_exec($ch);
if (curl_getinfo($ch, CURLINFO_HTTP_CODE) == 510) {
    echo "Not Extended";

Python Request and Response Example

Python script sending a request without the required extensions and handling a 510 Not Extended response:

import requests
response = requests.get('')
if response.status_code == 510:
    print("Not Extended")

Apache Configuration for HTTP 510 Not Extended

Configuring Apache to handle 510 errors:

# Apache Configuration Example
ErrorDocument 510 "Not Extended"

NGINX Configuration for HTTP 510 Not Extended

NGINX configuration for handling 510 errors:

# NGINX Configuration Example
error_page 510 /510.html;
location = /510.html {
    return 510 "Not Extended";

HTTP 509 Bandwidth Limit Exceeded (Apache) HTTP 511 Network Authentication Required


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