HTTP 409 Conflict vs 431 Request Header Fields Too Large
Both HTTP 409 (Conflict) and 431 (Request Header Fields Too Large) belong to the 4xx Client Error category. 409 indicates that the request conflicts with the current state of the server. Often due to concurrent modification or business rule violations. 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 request conflicts with the current state of the server. Often due to concurrent modification or business rule violations.
When You See It
When trying to create a resource that already exists, or updating a resource that was modified by another request.
How to Fix
Refresh the resource state, resolve conflicts, and retry. Use ETags for optimistic concurrency.
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 409: The request conflicts with the current state of the server. Often due to concurrent modification or business rule violations.
HTTP 431: The server refuses to process the request because an individual header field or all headers collectively are too large.
You encounter 409 when when trying to create a resource that already exists, or updating a resource that was modified by another request.
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 409 (Conflict): Refresh the resource state, resolve conflicts, and retry. Use ETags for optimistic concurrency. For 431 (Request Header Fields Too Large): Reduce header sizes. Clear excessive cookies. Use shorter tokens.