HTTP 226 IM Used vs 304 Not Modified
HTTP 226 (IM Used) is a 2xx Success response, while 304 (Not Modified) is a 3xx Redirection response. 226 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. In contrast, 304 means that the resource has not been modified since the last request. The client can use its cached copy.
Description
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.
When You See It
When using delta encoding to reduce bandwidth.
How to Fix
Rarely encountered. The response uses Instance Manipulations (IM) as specified.
Description
The resource has not been modified since the last request. The client can use its cached copy.
When You See It
When the browser cache is still valid (If-None-Match / If-Modified-Since headers match).
How to Fix
No fix needed. This saves bandwidth by confirming the cached version is still current.
Key Differences
226 is a 2xx Success response, while 304 is a 3xx Redirection response.
HTTP 226: 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.
HTTP 304: The resource has not been modified since the last request. The client can use its cached copy.
You encounter 226 when when using delta encoding to reduce bandwidth.
You encounter 304 when when the browser cache is still valid (If-None-Match / If-Modified-Since headers match).
When to Use Which
For 226 (IM Used): Rarely encountered. The response uses Instance Manipulations (IM) as specified. For 304 (Not Modified): No fix needed. This saves bandwidth by confirming the cached version is still current.