HTTP 304 Not Modified vs 505 HTTP Version Not Supported
HTTP 304 (Not Modified) is a 3xx Redirection response, while 505 (HTTP Version Not Supported) is a 5xx Server Error response. 304 indicates that the resource has not been modified since the last request. The client can use its cached copy. In contrast, 505 means that the server does not support the HTTP version used in the request.
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 server does not support the HTTP version used in the request.
When You See It
When a client uses an HTTP version the server doesn't support.
How to Fix
Use a supported HTTP version (typically HTTP/1.1 or HTTP/2).
Key Differences
304 is a 3xx Redirection response, while 505 is a 5xx Server Error response.
HTTP 304: The resource has not been modified since the last request. The client can use its cached copy.
HTTP 505: The server does not support the HTTP version used in the request.
You encounter 304 when when the browser cache is still valid (If-None-Match / If-Modified-Since headers match).
You encounter 505 when when a client uses an HTTP version the server doesn't support.
When to Use Which
For 304 (Not Modified): No fix needed. This saves bandwidth by confirming the cached version is still current. For 505 (HTTP Version Not Supported): Use a supported HTTP version (typically HTTP/1.1 or HTTP/2).