The HTTP 405 "Method Not Allowed" status code is a client error response that signifies a mismatch between the action you requested and the capabilities of the target resource. Essentially, the web server understands the request method (like GET, POST, PUT, or DELETE) but is explicitly configured to disallow that specific method for the URL you are trying to access.
🔑 The Core Problem
This error is fundamentally about resource-specific configuration, not general server availability or authorization:
Server Recognition: The server is functioning and knows what the request method is.
Method Prohibition: The specific resource at that URL has rules that forbid the use of the requested method.
📝 Common Example
A common scenario involves attempting to submit data to a resource that is designed only for reading:
If you send a POST request (used to submit data, like a form) to a URL that is only configured to accept GET requests (used to retrieve information), the server will return a 405 error.
The server is effectively saying, "I know you want to create something here, but this address is read-only."
🧭 The Crucial "Allow" Header
A key requirement for a server sending a 405 response is the inclusion of the Allow HTTP header in the response.
The
Allowheader is intended to act as a guide, listing all the HTTP methods that are supported for that specific resource.For example, a 405 response might include the header:
Allow: GET, HEAD. This tells the client, "You can only retrieve or check headers here."
This information allows the client application or developer to correct the request and interact with the resource using a supported method, resolving the "Method Not Allowed" issue.
