HTTP 226 IM Used


The HTTP 226 IM Used status code is used to indicate that the server has fulfilled a GET request for the resource, and the response is a representation of the result of one or more instance-manipulation operations applied to the current instance.


The HTTP 226 response is typically used in conjunction with the Instance Manipulations (IM) header to indicate partial updates to a cached resource.


Client Behavior:

  1. Send Request: The client sends a GET request with the IM header indicating support for instance manipulations.
  2. Receive Response: The client receives the HTTP 226 status code along with the updated content.

Server Behavior:

  1. Process Request: The server processes the request and applies instance manipulations to the resource.
  2. Send Response: The server sends a 226 IM Used response with the result of the applied manipulations.


  • Delta Encoding: Often used in delta encoding scenarios to send updates to previously cached data.
  • Partial Updates: Utilized to send partial updates to clients to reduce bandwidth and improve efficiency.

Sequence Diagram

Illustrating the process for an HTTP 226 response:

    participant Client
    participant Server as Web Server

    Note over Client: Client sends a GET request with IM header
    Client->>Server: GET /resource HTTP/1.1
    Note over Server: Server applies instance manipulations
    Server->>Client: HTTP/1.1 226 IM Used

Curl Request and Response Example

Requesting a resource with instance manipulations using Curl:

curl -i -H "A-IM: feed"
# Expected response: HTTP/1.1 226 IM Used

PHP cURL Request and Response Example

PHP script using cURL to request a resource with instance manipulations:

$ch = curl_init('');
curl_setopt($ch, CURLOPT_HTTPHEADER, array('A-IM: feed'));
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
$response = curl_exec($ch);
if (curl_getinfo($ch, CURLINFO_HTTP_CODE) == 226) {
    echo "Resource with instance manipulations received.";

Python Request and Response Example

Python script to send a GET request with instance manipulations and handle a 226 IM Used response:

import requests
headers = {'A-IM': 'feed'}
response = requests.get('', headers=headers)
if response.status_code == 226:
    print("Resource with instance manipulations received")

Apache Configuration for HTTP 226 IM Used

Configuring Apache to support HTTP 226 responses for instance manipulations:

<VirtualHost *:80>
    # Configuration directives for instance manipulations...

NGINX Configuration for HTTP 226 IM Used

Setting up NGINX to handle HTTP 226 responses for resources with instance manipulations:

server {
    listen 80;
    location /resource {
        # Directives for handling instance manipulations
        # ...

HTTP 208 Already Reported (WebDAV) HTTP 300 Multiple Choices


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