Is a 304 response an error?
No. It means the cached copy is still valid, so the server skipped sending the body. The browser displays the content it already has.
HTTP 304 NOT MODIFIED
The cached copy is still valid, so no body is sent. Answer to If-None-Match or If-Modified-Since. 304 belongs to the 3xx redirection class and is defined in RFC 9110.
Loading the workbench.
About HTTP 304
What Does HTTP 304 Not Modified Mean?
The cached copy is still valid, so no body is sent. Answer to If-None-Match or If-Modified-Since. The code is registered with IANA and defined in RFC 9110.
Redirection: the client must take another step to finish the request. Every code from 300 to 399 shares that general meaning, so a client that does not recognise 304 must treat it like 300.
When Do You See a 304 Response?
304 Not Modified is the answer to a conditional GET or HEAD when the client's cached copy is still current. The browser sends If-None-Match with the stored ETag, or If-Modified-Since with the stored date, and the server replies 304 with no body, saving the download. You see many of them in the DevTools network panel on reloads. A 304 is a success: the browser shows its cached copy.
How Do You Handle a 304?
Servers must not send a body, and should include the headers that would have accompanied a 200, especially ETag, Cache-Control, Expires, Vary, and Date, so caches can refresh their stored metadata. If 304s never appear, check that responses carry a validator and that the ETag is stable across servers behind the load balancer. The 2http Cache lane checks whether an If-None-Match would match.
What Does a 304 Response Look Like?
HTTP/1.1 304 Not Modified
ETag: W/"5e15153d-120f"
Cache-Control: max-age=0, must-revalidate
Date: Tue, 10 Nov 2026 18:00:00 GMT304 is not cacheable by default: a browser or CDN stores it only when Cache-Control or Expires explicitly allows it.
To inspect a real one without sending it anywhere:
- Copy the response headers from your browser Network tab, or from
curl -i. - Paste them into the Header decoder to see every header explained.
- Check caching in the Cache lane and the Location target in the decoder.
Which Status Codes Are Related to 304?
- 200 OK: The request succeeded. The body depends on the method.
- 412 Precondition Failed: An If-Match or If-Unmodified-Since condition was false. Used for optimistic locking.
- 206 Partial Content: Only the requested byte range is returned. Used for resumable downloads and video seeking.
Browse every code on the HTTP status codes page.
What Other Lanes Are in the Reference Section?
- HTTP status codes: Every IANA-registered status code, with a page per code.
- MIME types: File extensions to Content-Type, searchable both ways, plus a Content-Type parser.
- HTTP methods: GET, POST, PUT, PATCH, DELETE and the rest: safe, idempotent, cacheable.
Elsewhere in 2http: Header decoder, Cookie decoder, Cache-Control decoder, CORS checker, User-agent parser, and all eleven lanes on the 2http home page. Part of the 2suite.io privacy-first ecosystem.
Frequently Asked Questions
Why do I get 200 instead of 304 every time?
Usually the response has no ETag or Last-Modified, the ETag changes on every request, or different servers generate different ETags for the same file. Fix the validator and 304s will start appearing.
Is HTTP 304 an error?
No. 304 is a redirection response, not an error.
Is a 304 response cacheable by default?
No. Caches store a 304 only when Cache-Control or Expires explicitly allows it.
How Can You Verify That Nothing Leaves This Browser?
You do not have to take our word that your headers stay here. Developer tools show every request a page makes, so you can watch this page work and confirm that nothing is sent. The check takes under a minute.
- Open your browser developer tools with
F12, orCmd+Option+Ion a Mac, and select the Network tab. - Reload the page and let it finish. You will see the page's own files, its web fonts, and one anonymous page-view request. Nothing has been typed yet, so none of them can contain your headers.
- Click the clear icon in the Network tab so that the log is empty.
- Paste real headers into any lane and read the result.
- Look at the Network tab again. It is still empty. For extra proof, turn on offline mode after the page loads and every lane keeps working.
Only two things can add a line to that log, and neither carries your headers. Submitting the feedback form sends the vote and comment you typed. Typing characters in a script the page has not displayed yet, such as Cyrillic or Greek, can make the browser fetch the matching font file, and that request names only the font.
2http never sends a request on your behalf: the request builder writes code for you to run, and the meta inspector reads source you paste instead of fetching a URL. The production site also sends a Content-Security-Policy header that tells your browser to refuse connections to anywhere except this site and the anonymous analytics endpoint.