Allow Header

What is the Allow header?

The Allow response header lists the set of HTTP methods supported by a resource. It is required on any 405 Method Not Allowed response, and is equally standard on a successful OPTIONS response, where it’s the primary way a client discovers what a resource supports.

API Usage & Best Practices

• Always send on 405: When rejecting a request due to an unsupported method, always include Allow: GET, POST, HEAD (matching the supported methods for that path).
• Also send on OPTIONS: A 200 OK response to OPTIONS should carry the same header so clients can probe supported methods without triggering an error.
• Do not include trailing commas: The methods should be comma-separated, like GET, POST, PUT.

Examples

HTTP/1.1 405 Method Not Allowed
Allow: GET, HEAD
Content-Type: application/problem+json