HTTP 409 Conflict vs 411 Length Required
Both HTTP 409 (Conflict) and 411 (Length Required) 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, 411 means that the server refuses to accept the request without a Content-Length header.
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 accept the request without a Content-Length header.
When You See It
When sending a request body without specifying Content-Length.
How to Fix
Include a Content-Length header in your request.
Key Differences
HTTP 409: The request conflicts with the current state of the server. Often due to concurrent modification or business rule violations.
HTTP 411: The server refuses to accept the request without a Content-Length header.
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 411 when when sending a request body without specifying Content-Length.
When to Use Which
For 409 (Conflict): Refresh the resource state, resolve conflicts, and retry. Use ETags for optimistic concurrency. For 411 (Length Required): Include a Content-Length header in your request.