HTTP 226 IM Used
The server has fulfilled a GET request for the resource, and the response represents the result of one or more instance-manipulations.
2xx Success
226
IM Used
Description
The 226 IM Used status code indicates 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-manipulations applied to the current instance. The actual current instance might not be available except by combining this response with other previous or future responses, as appropriate for the specific instance-manipulation(s). IM stands for Instance Manipulation. The response headers will include an IM header indicating the type of manipulation applied, and may include a Delta-Base header indicating the base instance.
When Is It Used?
Used with HTTP delta encoding to transmit only the differences between resource versions rather than the full resource. This reduces bandwidth when a resource has been slightly modified since the last request.
Example Response
HTTP/1.1 226 IM Used
IM: vcdiff
Date: Tue, 20 Feb 2026 12:00:00 GMT
ETag: "abc123"