HTTP 304 Not Modified vs 405 Method Not Allowed
HTTP 304 (Not Modified) is a 3xx Redirection response, while 405 (Method Not Allowed) is a 4xx Client Error response. 304 indicates that the resource has not been modified since the last request. The client can use its cached copy. In contrast, 405 means that the HTTP method is not allowed for the requested resource. The response includes an Allow header listing valid methods.
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.
Description
The HTTP method is not allowed for the requested resource. The response includes an Allow header listing valid methods.
When You See It
When sending POST to a read-only endpoint, or DELETE to a non-deletable resource.
How to Fix
Check the Allow response header for supported methods. Use the correct HTTP method.
Key Differences
304 is a 3xx Redirection response, while 405 is a 4xx Client Error response.
HTTP 304: The resource has not been modified since the last request. The client can use its cached copy.
HTTP 405: The HTTP method is not allowed for the requested resource. The response includes an Allow header listing valid methods.
You encounter 304 when when the browser cache is still valid (If-None-Match / If-Modified-Since headers match).
You encounter 405 when when sending POST to a read-only endpoint, or DELETE to a non-deletable resource.
When to Use Which
For 304 (Not Modified): No fix needed. This saves bandwidth by confirming the cached version is still current. For 405 (Method Not Allowed): Check the Allow response header for supported methods. Use the correct HTTP method.