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The 405 error and how to fix it
5 min read
The 405 error, formally known as the "405 Method Not Allowed" error, is an HTTP status code that indicates that the method used in the request is not allowed by the server for the targeted resource. While it may seem daunting to beginners or even experienced developers, understanding its cause and solutions can streamline troubleshooting and improve website functionality.
This article explores the nature of the 405 error from a number of angles, including its technical background, common causes, and practical solutions.
What is a 405 Error?
The 405 error occurs when a client sends a request using an HTTP method (such as GET, POST, PUT, DELETE, etc.) that the server does not allow for the requested resource. Instead of processing the request, the server responds with a 405 Method Not Allowed message.
The 405 status code is part of the HTTP/1.1 standard and is often accompanied by additional information in the response body to guide developers toward resolving the issue. For example:
HTTP/1.1 405 Method Not Allowed
Content-Type: text/html
Allow: GET, HEAD
In this example, the server explicitly states that only the GET and HEAD methods are allowed for the requested resource, rejecting other methods such as POST or DELETE.
Common causes of a 405 error
1. Incorrect HTTP methods
One of the most common causes of a 405 error is sending a request using an unsupported HTTP method. For example, attempting to update a resource using a POST method when the server expects a PUT method can trigger the 405 status code.
Example scenario:
A client tries to send form data using POST, but the server only accepts GET requests for that endpoint.
2. Server configuration issues
Web server misconfigurations in platforms such as Apache, Nginx or IIS can also result in a 405 Method Not Allowed error. These configurations determine which HTTP methods are allowed for each resource.
For example:
An Apache server may have a .htaccess file that explicitly denies certain methods for security reasons.
3. Incorrect URL routing
In modern applications, especially those using frameworks such as Django, Flask or Express.js, routing mismatches between the URL and the corresponding controller can result in a 405 HTTP error.
For example:
A developer could configure a route to only accept PUT requests, but accidentally send a POST request.
4. CORS policies
Cross-origin resource sharing (CORS) policies are another potential culprit. If the server disallows methods for cross-origin requests, a 405 response code may be returned.
For example:
A client application hosted on example.com sends a DELETE request to an API hosted on api.example.com, but the server restricts such methods to external origins.
Other useful articles in our Blog:
- How to Fix "Connection Refused" Error
- Everything you need to know about 404 errors
- 502 Bad Gateway Error: What It Is and How to Fix It
- Pip: Python Package Management Basics
How to Fix the 405 Error
Step 1: Verify the HTTP Method
Make sure that the method you are using matches the server's expectations. If you're working with APIs, check the API documentation to confirm the supported methods. For example, if you're sending a POST request but the API requires PUT, adapt your code accordingly.
Step 2: Inspect Server Configuration
For server administrators, check the server’s configuration files. Depending on the server type, here are some steps:
Apache: Examine .htaccess or httpd.conf for directives like LimitExcept or RewriteRule that may restrict specific methods.
Nginx: Check the nginx.conf file for limit_except directives.
IIS: Verify the HTTP verbs allowed in the server's handler mappings.
Ensure the correct methods are enabled for the required resources.
Step 3: Debug Application Code
In applications, mismatched routes often cause the 405 error. Review your routing configuration to ensure that the correct methods are bound to the intended endpoints.
Example in Flask (Python):
from flask import Flask, request
app = Flask(__name__)
@app.route('/submit', methods=['POST'])
def submit_form():
return "Form submitted successfully!"
if __name__ == "__main__":
app.run()
In this case, accessing /submit with any method other than POST will result in a 405 error.
Step 4: Review CORS Policies
If the issue involves cross-origin requests, check the server’s CORS settings. Ensure that all required methods (e.g., GET, POST, DELETE) are listed in the Access-Control-Allow-Methods header.
Example CORS header:
Access-Control-Allow-Methods: GET, POST, PUT, DELETE
Step 5: Check File Permissions
On static sites, a 405 error can occur if the server cannot handle the requested method due to file permission issues. Ensure that files and directories have the correct permissions for web access.
Step 6: Consult Server Logs
When troubleshooting, the server logs are invaluable. Logs often provide additional details about the root cause of the 405 response code. For Apache, logs are typically located in /var/log/apache2/, while Nginx logs can be found in /var/log/nginx/.
Preventing 405 Errors
Standardize API Documentation: Ensure APIs are well-documented, specifying permissible methods for each endpoint.
Test HTTP Methods: Use tools like Postman or curl to test endpoints and verify supported methods during development.
Implement Proper Error Handling: Configure custom error pages or responses to provide actionable guidance for users encountering the 405 Method Not Allowed POST issue.
Conclusion
The 405 error is a common but avoidable problem in web hosting and application development. It serves as a reminder of the importance of matching client requests with server expectations. By understanding the causes - from misconfigured routes to improper CORS settings - and applying targeted fixes, developers and administrators can effectively resolve the 405 Method Not Allowed error.
Whether you're debugging application code, adjusting server configurations or testing HTTP methods, a systematic approach will help you eliminate this error and ensure seamless website functionality.
