4xx Client error
HTTP 425 Too Early
The server won’t process a request sent as TLS 1.3 early data (0-RTT), because such data can be replayed by an attacker. The client should send it again after the TLS handshake is complete.
Defined in RFC 8470, section 5.2(opens in a new tab)
//_01 Uptime checks
Is 425 up or down for a monitor?
Uptimecheck HTTP monitor
Default settings
Down. It is outside the default 200–399 range, so a monitor reports an outage once a second check confirms it. If 425 is the answer you expect from that URL, add it to the monitor’s expected status codes.
Is it down? checker
Free, at /is-it-down/
Up. The checker counts any answer below 500 as the site answering: a 425 comes from a server that is running.
//_02 Causes and fixes
Why you see 425 and what to do
Typical causes
- TLS 1.3 0-RTT turned on at a server or CDN that is careful about which requests it accepts early.
If you run the site
- Only accept early data for requests that are safe to repeat, such as plain GETs.
If you’re a visitor
- Reload the page.
Know the moment your site stops answering as it should
An Uptimecheck monitor requests your page as often as every minute, checks the status code against the ones you expect, confirms a failure with a second check and then alerts you.
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Questions
What does HTTP 425 mean?
The server won’t process a request sent as TLS 1.3 early data (0-RTT), because such data can be replayed by an attacker. The client should send it again after the TLS handshake is complete.
Does an uptime monitor count 425 as down?
Down. It is outside the default 200–399 range, so a monitor reports an outage once a second check confirms it. If 425 is the answer you expect from that URL, add it to the monitor’s expected status codes.
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