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HTTP 425 Too Early

Updated Free mock REST & WebSocket APIs

HTTP 425 Too Early — The server won't process a request sent in TLS 1.3 early data (0-RTT) because it might be replayed.

Class
4xx Client Error
Defined in
RFC 8470
Official
Yes (IANA registry)
Cacheable by default
No (unless Cache-Control/Expires say so)
Safe to retry
Yes, after a delay (respect Retry-After)

Try it: get a real 425 response

Our test endpoint answers every request with 425 Too Early.

curl -i https://mockfox.dev/api/status/425

Use it in tests, health-check monitors or to see how your client handles a 425. Add ?delay=2000 to slow it down.

What does HTTP 425 mean?

TLS 1.3 lets clients send data in the first flight (0-RTT), but that data can be replayed by an attacker. A server or CDN that receives a non-idempotent request in early data (marked Early-Data: 1 by intermediaries) can answer 425 and the client automatically retries after the handshake completes.

How to fix 425

  1. Visitors: Reload the page, check the address for typos, and clear the site's cookies. If it persists, the site owner needs to fix it.
  2. Developers: Read the response body and server logs for details, fix the request (method, headers, body, credentials) and return a clear error message to clients.

Example 425 response

HTTP/1.1 425 Too Early
Content-Type: application/json

{"status":425,"error":"Too Early"}

4xx Client Error: The request contains an error or can't be fulfilled — fix the request before retrying. See the full list of HTTP status codes.

Related status codes

Related tools

Frequently asked questions

What does HTTP 425 Too Early mean?

The server won't process a request sent in TLS 1.3 early data (0-RTT) because it might be replayed.

Is 425 a client or a server error?

425 is a 4xx code, so it signals a problem with the request (as seen by the server). Retrying the identical request usually gives the same result.

Where is 425 defined?

In RFC 8470. It's listed in the IANA HTTP Status Code Registry.

How can I test how my app handles a 425?

Call https://mockfox.dev/api/status/425 — it responds with 425 to any method, with CORS enabled. Add ?delay=2000 to simulate a slow response.