HTTP 409 Conflict

The request conflicts with the current state of the target resource.

Use 409 for edit conflicts, duplicate unique values, or state transitions that cannot currently be applied.

httpstatus codevalidationconcurrency

Response (http)

HTTP/1.1 409 Conflict

Use 409 for edit conflicts, duplicate unique values, or state transitions that cannot currently be applied.

Common mistakes

Returning 409 without identifying which state or version the request conflicted with.

Registry reference: RFC9110, Section 15.5.10

Sources