226 IM Used

The server applied delta encoding and is returning the changes rather than the whole resource.

Code: 226
Reason phrase: IM Used
Class: 2xx Success
Defined in: RFC 3229 section 10.4.1
Cacheable by default: No

What it means

Success: the request was received, understood and accepted.

Common causes. Very rare: clients that support HTTP delta encoding (RFC 3229).

What to do. Nothing.

How clients and crawlers treat it

Caching. Not cacheable by default (RFC 9110 section 15.1 does not list it). A cache stores it only when the response says so with Cache-Control or Expires.

Example response

HTTP/1.1 226 IM Used
Content-Type: text/plain; charset=utf-8

IM Used

How to send 226

nginx

location /example {
    return 226 'IM Used';
}

PHP

http_response_code(226);
echo 'IM Used';
exit;

Node.js

res.writeHead(226, { 'Content-Type': 'text/plain' });
res.end('IM Used');

Python (Flask)

# in a view function
return 'IM Used', 226

Change the paths to suit. In nginx, add_header needs always to apply to error responses.

Related codes

All status codes · All 2xx codes

Names and numbers from the IANA HTTP Status Code Registry. Google Search behaviour as documented by Google Search Central.