HTTP Error 405: What's behind it and how to fix it?

When a client like a browser requests a webpage, the server responds with content and a status code. An HTTP error occurs when the website cannot be created or loaded for a specific reason. The HTTP Error 405 stands for "Method not allowed" and indicates that the client is requesting an action that the web server is blocking or unable to perform. As a result, it cannot deliver the desired content and generally points to a reason - in this case, the error 405.

What HTTP errors are there?

By looking at the first digit of a status code, you can already identify the type of response. A 1XX code contains purely informational statements, while 2XX indicates successful processing and 3XX stands for redirections. Starting from error 400, the status indicates that the webpage could not be loaded, with 4XX indicating a cause by the client and 5XX indicating one by the server. Some of the most common issues are:

• HTTP Error 400: Bad Request occurs due to incorrect syntax
• HTTP Error 401: Unauthorized requires authentication through a login
• HTTP Error 403: Forbidden means there are no access rights in general
• HTTP Error 404: Not found indicates a non-existent webpage
• HTTP Error 405: Method not Allowed when the client requests a forbidden method
• HTTP Error 408: Request Timeout signals a too long waiting time
• HTTP Error 500: Internal Server Error means the server cannot generate a response
• HTTP Error 522: Connection timed out indicates a timeout on the server side

What is the HTTP Error 405: Method not allowed?

Under HTTP, there are different methods that allow actions to be performed on the web server. The most well-known among them are GET for requesting data from the server and POST for transmitting data from the client. A server can explicitly allow or block these methods if they are not needed or pose a security risk. The HTTP Error 405 occurs when a request demands a method from the server that it does not support. It is a client error like Error 403, as from the server's perspective, the visitor is trying to access a blocked resource or using a method that is not allowed. Therefore, it recognises that it is functioning correctly and the client is sending an incorrect request.

What is the solution for an HTTP Error 405?

While, for example, Error 403 indicates a clear cause or Error 401 gives the visitor the opportunity to identify themselves through an input field, many other status codes like Error 400, Error 405, and Error 408 are very unspecific. They only indicate that a problem is occurring but do not specify the direct cause. Consequently, finding a solution can be challenging. However, these error messages often occur in specific situations or in connection with a particular configuration. Regardless, there are three different ways that offer a quick and reliable solution for Error 405:

• Allowing the HTTP method
• Using a different HTTP method in the source code
• Bypassing MIME types blocked by providers

Current versions of the Apache 2 web server have a module named mod_allowmethods, which can be activated in the configuration for one or more URLs. This simply requires an entry AllowMethods in the container, for example:

AllowMethods GET POST OPTIONS

At times, it may happen that the source code simply uses the wrong method. The specific location can be identified using tools like the developer tool in Google Chrome or the developer tools in Mozilla Firefox and replaced for testing. If the Error 405 disappears, the responsible PHP script in the source code needs to be rewritten.

Some providers exclusively allow certain HTTP methods for specific file types (MIME). For example, POST is often blocked for HTML files to enhance security but is permitted for PHP. Since PHP scripts can contain HTML code, all that needs to be done is to change the extension from .html to .php to eliminate the Error 405.

Photo: Gerd Altmann from Pixabay