# POST method > Submits an entity to the specified resource, often causing a change in state or side effects on the server. Source: https://apiguide.dev/methods/post Safe: no Idempotent: no Cacheable: no Defined in: RFC 9110, Section 9.3.3 Updated: 2026-10-14 ## What is the POST method? The `POST` method submits data to the server to create a new resource, execute a controller action, or trigger side effects. ## API Usage & Best Practices * **Non-idempotent**: Multiple identical POST requests will result in multiple resource creations or side effects. If a client submits a payment request twice, they may be charged twice. * **Protect with Idempotency Keys**: Use a custom header like `Idempotency-Key` to prevent duplicate creations due to network timeouts. * **Redirect on Success**: Standard practice for resource creation is to return a `201 Created` response containing a `Location` header pointing to the new resource. ## Common Response Codes * **200 OK**: The request succeeded but the endpoint doesn't create a resource (e.g. a search or action controller returning a result body). * **201 Created**: The resource was successfully created. * **202 Accepted**: The request was accepted and queued for async background processing. * **400 Bad Request**: The request body is structurally malformed (invalid JSON). * **409 Conflict**: The resource being created collides with an existing one (e.g. a unique constraint violation). * **422 Unprocessable Content**: The request body was parsed but failed input validation.