425 Too Early
4xx Client Error
RFC 8470 Experimental
Don't replay this — it might not be safe.
What 425 Too Early means {#what}
The server refuses to process a request that might be replayed. Related to TLS 1.3 early data (0-RTT), where replaying requests could cause unintended side effects. An experimental safeguard.
When you’ll see a 425 {#when}
- Servers rejecting 0-RTT TLS early data for non-idempotent requests
- Edge cases in TLS 1.3 connection handling