The HTTP 304 Not Modified client redirection response code indicates that there is no need to retransmit the requested resources. It is an implicit redirection to a cached resource. This happens when the request method is safe, like a GET or a HEAD request, or when the request is conditional and uses a If-None-Match or a If-Modified-Since header.
If the equivalent 200 OK response would have included the headers Cache-Control, Content-Location, Date, ETag, Expires, and Vary.
Many developer tools' network panels of browsers create extraneous requests leading to 304 responses, so that access to the local cache is visible to developers.
304 Not Modified
| Specification | Title |
|---|---|
| RFC 7232, section 4.1: 304 Not Modified | Hypertext Transfer Protocol (HTTP/1.1): Conditional Requests |
| Feature | Chrome | Edge | Firefox | Internet Explorer | Opera | Safari | Servo |
|---|---|---|---|---|---|---|---|
| Basic Support | (Yes) | (Yes) | (Yes) | (Yes) | (Yes) | (Yes) | (Yes) |
| Feature | Android | Chrome for Android | Edge Mobile | Firefox for Android | IE Mobile | Opera Mobile | Safari Mobile |
|---|---|---|---|---|---|---|---|
| Basic Support | (Yes) | (Yes) | (Yes) | (Yes) | (Yes) | (Yes) | (Yes) |
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https://developer.mozilla.org/en-US/docs/Web/HTTP/Status/304