HTTP Status Code

226 IM Used

Success

The server has fulfilled a GET request and the response is a representation of the result of one or more instance-manipulations applied to the current instance.

HTTP status code reference, response example, common causes, fixes, and related status codes.

What does HTTP 226 IM Used mean?

HTTP 226 IM Used is a status code sent by a server to indicate the result of an HTTP request.

Status codes help browsers, APIs, apps, and backend systems understand whether a request succeeded, failed, was redirected, or needs additional action.

In practice, HTTP 226 IM Used usually appears when a server responds under specific request, validation, permission, or infrastructure conditions.

Response example

HTTP/1.1 226 IM Used
  IM: gzip

HTTP example

HTTP/1.1 226 IM Used

Common causes

Delta encoding applied to a response
HTTP delta compression using RFC 3229

How to fix it

No fix needed — the client requested delta encoding and received it
Ensure client-side delta reconstruction logic is correct

Common mistakes

Assuming the status code alone explains the full backend issue
Ignoring related response headers that add important context
Treating temporary errors as permanent failures
Retrying too aggressively without checking the cause
Debugging the frontend only when the problem is server-side

How browsers and APIs use it

Browsers, APIs, and backend services use HTTP status codes to understand the outcome of a request. Depending on the status code, an application may render content, retry a request, redirect the user, show an error, or trigger a different flow in the client or server.

Practical developer insight

226 IM Used is defined in RFC 3229 for HTTP delta encoding, a mechanism to send only the changes between versions of a resource. Most developers will never encounter this status code — it has extremely low adoption in practice and is mostly a curiosity in the HTTP spec.

Related status codes

HTTP 200