When something breaks on your site you’ll typically encounter what is called an HTTP status code.

These are delivered to your browser in the HTTP header and to help you troubleshoot what might be wrong. Some status codes you’re probably familiar with include 404 “not found” errors or a 301 redirect for SEO purposes.

Today we’re going to discuss a less common status code, and that is the 501 not implemented error. Follow the steps and recommendations below to resolve it.

What is the HTTP 501 Not Implemented Error?

The Internet Engineering Task Force (IETF) defines the 501 Not Implemented as:

The 501 (Not Implemented) status code indicates that the server does not support the functionality required to fulfill the request. This is the appropriate response when the server does not recognize the request method and is not capable of supporting it for any resource.

A 501 response is cacheable by default; i.e., unless otherwise indicated by the method definition or explicit cache controls.

The 501 not implemented error indicates that the server does not support the functionality required to fulfill the request. This is the appropriate response when the server does not recognize the request method and is not capable of supporting it for any resource (RFC7231, section 6.6.2). A 501 response is also cacheable by default.

Due to the various browsers, web servers, and operating systems, a 501 not implemented error can present itself in a number of different ways. But they all have the same meaning. Below are just a couple of the many different variations you might see on the web:

  • “501 Not Implemented”
  • “Error 501”
  • “HTTP 501”
  • “HTTP Error 501 Not implemented”
  • “The server either does not recognize the request method, or it lacks the ability to fulfill the request.”
501 not implemented error in browser
501 not implemented error in browser

Check Out Our Video Guide to The 501 Error

501 Errors Impact on SEO

Unlike 503 errors, which are used for maintenance mode and tell Google to check back at a later time, a 501 error can have a negative impact on SEO if not fixed right away. If your site is only down for say 10 minutes and it’s being crawled consistently a lot of times the crawler will simply get the page delivered from cache. Or Google might not even have a chance to re-crawl it before it’s back up. In this scenario, you’re completely fine.

However, if the site is down for an extended period of time, say 6+ hours, then Google might see the 501 error as a site level issue that needs to be addressed. This could impact your rankings. If you’re worried about repeat 501 errors you should figure out why they are happening to begin with. Some of the solutions below can help.

How to fix the HTTP 501 Not Implemented Error

A 501 not implemented error is almost always a problem with your web server. There are a few things you can do on your side to try and resolve it, but typically this is the type of error where you’ll need to reach out to your host to fix.

1. Try Reloading the Page

One of the easiest and first things you should try when encountering a 501 not implemented error is to simply wait a minute or so and reload the page (F5 or Ctrl + F5). It could be that the host or server will resolve the issue While you’re waiting, you could also quickly try a different browser to rule that out as an issue.

Another thing you can do is to paste the website into downforeveryoneorjustme.com. This website will tell you if the site is down or if it’s a problem on your side.


2. Clear Your Browser Cache

Whenever you encounter issues like these it can be good to clear your browser cache. Below are instructions on how to clear cache in the various browsers:

3. Disable Proxy Settings

This is very rare, but sometimes you might see a 501 error if you are utilizing a proxy service. Or one might have been set without you even knowing it. Follow these tutorials on how to disable or check to ensure no proxy settings are enabled:

Chrome proxy settings
Disable Chrome proxy settings

4. Reach Out To Your Host

Unlike some other HTTP status codes where there is a lot of troubleshooting you can do yourself, 501 errors are almost always an issue on the web server. They aren’t usually caused by a bad plugin or caching issue. Therefore, if it doesn’t resolve itself within a few minutes we recommend simply reaching out to your host. You can also check your host’s status page.

Typical causes of this error on the server might include:

  • There was a bad update to the server causing it to not properly respond to the browser’s request.
  • There is a misconfiguration in NGINX that needs to be fixed by an engineer.
  • The server you’re attempting to access may be overwhelmed and therefore isn’t able to properly generate the request.
  • It could also be a billing issue. If you didn’t pay your hosting bills, they might default your site to 501 status before removing the account altogether, giving you another chance to resolve the issue.

At Kinsta, a 501 error can also be due to the fact that your staging site has stopped. Under your site’s Info tab you will see the option to “Start staging environment.”

Start staging environment
Start staging environment

If for some reason you’re still having issues, simply open a support ticket and we’ll get it fixed immediately.

Send WordPress support ticket
Send support ticket

If you are worried about these happening on your site in the future, you can also utilize a tool like updown.io to monitor and notify you immediately if they occur. It periodically sends an HTTP HEAD request to the URL of your choice. You can simply use your homepage. The tool allows you to set check frequencies of:

  • 15 seconds
  • 30 seconds
  • 1 minute
  • 2 minutes
  • 5 minutes
  • 10 minutes

It will send you an email if and when your site goes down. Here is an example below.

Email notification of 501 error
Email notification of 501 error

This can be especially useful if you’re on a shared host, who tend to overcrowd their servers. This can give you proof of how often your site might actually be doing down (even during the middle of the night). That’s why we always recommend going with an application, database, and managed WordPress host such as Kinsta.

If you want to keep your site in good shape, make sure to read our in-depth guide on WordPress maintenance.