HTTP 425 Too Early vs 431 Request Header Fields Too Large
Both HTTP 425 (Too Early) and 431 (Request Header Fields Too Large) belong to the 4xx Client Error category. 425 indicates that the server is unwilling to risk processing a request that might be replayed. Used with TLS 1.3 early data (0-RTT). Meanwhile, 431 means that the server refuses to process the request because an individual header field or all headers collectively are too large.
Description
The server is unwilling to risk processing a request that might be replayed. Used with TLS 1.3 early data (0-RTT).
When You See It
When a server rejects a request sent as TLS 1.3 early data due to replay risk.
How to Fix
Retry the request after the TLS handshake completes.
Description
The server refuses to process the request because an individual header field or all headers collectively are too large.
When You See It
When cookies accumulate to an excessive size, or a single header (like Authorization) is too long.
How to Fix
Reduce header sizes. Clear excessive cookies. Use shorter tokens.
Key Differences
HTTP 425: The server is unwilling to risk processing a request that might be replayed. Used with TLS 1.3 early data (0-RTT).
HTTP 431: The server refuses to process the request because an individual header field or all headers collectively are too large.
You encounter 425 when when a server rejects a request sent as TLS 1.3 early data due to replay risk.
You encounter 431 when when cookies accumulate to an excessive size, or a single header (like Authorization) is too long.
When to Use Which
For 425 (Too Early): Retry the request after the TLS handshake completes. For 431 (Request Header Fields Too Large): Reduce header sizes. Clear excessive cookies. Use shorter tokens.