HTTP 504 GATEWAY TIMEOUT

A proxy or gateway gave up waiting for the upstream server. 504 belongs to the 5xx server error class and is defined in RFC 9110.

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About HTTP 504

What Does HTTP 504 Gateway Timeout Mean?

A proxy or gateway gave up waiting for the upstream server. The code is registered with IANA and defined in RFC 9110.

Server error: the server failed to fulfill a valid request. Every code from 500 to 599 shares that general meaning, so a client that does not recognise 504 must treat it like 500.

When Do You See a 504 Response?

504 Gateway Timeout comes from a proxy, load balancer, or CDN that waited too long for the upstream server to respond. The app may be stuck on a slow database query, an external API call, a deadlock, or an expensive report, or the upstream may be unreachable at the network level. Default proxy timeouts are often 30 or 60 seconds, so long-running requests frequently surface as 504 even when the app eventually finishes.

How Do You Fix a 504?

Find what is slow: check application logs and traces for the request, slow query logs, and calls to third-party services. Move long jobs to a background queue and return 202 Accepted with a status URL instead of holding the connection. Raising the proxy timeout can help in the short term. Clients can retry idempotent requests with backoff, but should avoid retrying non-idempotent ones blindly.

What Does a 504 Response Look Like?

HTTP/1.1 504 Gateway Timeout
Server: cloudflare
Content-Type: text/html

504 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.

Which Status Codes Are Related to 504?

502 Bad Gateway: A proxy or gateway got an invalid response from the upstream server.
408 Request Timeout: The client took too long to send the request.
503 Service Unavailable: Overloaded or down for maintenance. Retry-After may say when it will return.
202 Accepted: The request was queued but not finished. Common for background jobs.

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

Does a 504 mean my request was not processed?

Not necessarily. The gateway gave up waiting, but the upstream server may still have finished the work. Be careful when retrying requests that change data.

How do I avoid 504 errors for slow operations?

Run long tasks asynchronously: accept the request with 202 Accepted, process it in the background, and let the client poll or receive a webhook when it finishes.

Is HTTP 504 an error?

Yes. 504 is a server error response: the server failed to handle a valid request, so retrying later may work.

Is a 504 response cacheable by default?

No. Caches store a 504 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, or Cmd+Option+I on 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.

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