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304 Not Modified

The HTTP 304 Not Modified status code tells clients that a cached resource is still valid and does not need to be downloaded again.

Published 16 Jul 2026 · HTTP Status Code

What is HTTP 304 Not Modified?

The 304 Not Modified response indicates that a cached version of a resource can still be used.

It improves performance by avoiding unnecessary data transfers.

Clients send conditional requests using headers such as:

If-None-Match
If-Modified-Since

If the resource has not changed, the server responds:

HTTP/1.1 304 Not Modified

304 responses are important when optimising performance and troubleshooting caching behaviour.

The 304 Not Modified response allows clients to reuse cached resources efficiently.

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