226 IM Used

What is HTTP 226?

This status code indicates that the server has fulfilled a GET request and the response represents the result of one or more instance manipulations applied to the current instance of the resource. Instance manipulations include delta encoding, where only the changes since the client's last version are sent rather than the full resource. This is an optimization for bandwidth, allowing efficient updates of cached resources.

Defined in RFC 3229

Common Causes

• The server applied delta encoding to send only the changes since the client's cached version
• An instance manipulation like vcdiff was used to reduce transfer size
• Feed aggregators requesting incremental updates to previously fetched content

How to Fix

• No fix needed; your client should apply the instance manipulation to reconstruct the full resource
• If your client cannot process the manipulation, remove the A-IM header from requests
• Verify your client supports the specific instance manipulation indicated in the IM response header