304Not Modified
Nothing has changed since you last fetched this, so use the copy you already have.
Browse all HTTP status codesWhen you see it
The single most useful code for performance. The browser asks whether its cached copy is still good, using an If-None-Match or If-Modified-Since header, and 304 answers yes with no body at all. A page can appear to reload while transferring almost nothing.
What to check
Seeing 304 in your network tab is good news, not a problem, and it is a frequent source of confusion when someone thinks a file failed to load. If you are trying to see a change and keep getting 304s, do a hard reload so the browser sends the request without the validation headers.
If a page never returns 304 and re-downloads everything on every visit, the server is not sending ETag or Last-Modified headers and every visitor is paying for it.
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