Practical Approach to Fix Error 521: Instant Troubleshooting

Error 521 is basically a Cloudflare based message that generally takes place when the WordPress website server is unable to make a connection with the Cloudflare.

Most importantly, it signifies that the web browser cannot connect to Cloudflare successfully.

Cloudflare always tries to connect to the site server of the website. However, you might receive a connection-related error in return during the process.

This is owing to the fact that Cloudflare becomes unable to connect to the website and it can’t exhibit the site to the visitor’s website thereby showing the error code 521.

However, if you follow this blog, you will get to know the possible causes and effective hacks to prevent this issue in one go.

Obvious Causes Behind the Error 521 Message

Error code 521 shows up owing to two different situations.

  1. It might happen that the server of the WordPress site is down. Even if all the other parameters are safe and the site server of WordPress is offline, it is impossible for the Cloudfare to establish the connection.
  2. Further, it might happen that the web browser is running but it may block Cloudfare’s request due to several reasons. Because of the operation of the Cloudfare, the server-side security solutions can easily block the IP address of the Cloudflare.

Since Cloudflare is termed as a reverse proxy server, all the traffic bypassed to the original server will show up. This is because it is coming from a small variety of Cloudflare IPs.

There are certain security solutions which might see a sudden surge in the traffic from a limited number of IP addresses.

When the above-mentioned situation pops up, it becomes impossible for the Cloudflare to connect and thereby puts up the error code 521.

Effective Resorts to Fix Error Notification 521 for Cloudflare and WordPress

Now you know the most obvious causes, let’s dig into the effective fixes to resolve the error 521 in WordPress.

Method 1: Examine Whether the Parent Server is Online

Before you move ahead, ensure that the site server of WordPress is online and operates properly. If the website is not online, there is no point in digging into the troubleshooting methods.

In order to examine this, run the cURL command. If you are a regular Mac user, you can execute this from the periphery.

Windows don’t come up with cURL installation. Therefore, if you like to install it, then the simpler approach is to check the automated tool.

All you have to do is to navigate to Here, signifies the actual IP address of the designated server.

Method 2: Whitelist all Cloudflare IP Ranges in the Firewall Server

If the site server of WordPress is working properly still you are witnessing the error code 521, then whitelist all the IP ranges of the Cloudflare to ensure that the server won’t block them.

Furthermore, ensure the fact that you are not blocking the IP address or the Firewall. Also, you have to make sure that the hosting company is not rating the limiting or blocking the IP requests coming from the IP addresses of Cloudflare.

If you don’t know how to do this, then you can seek professional help. This procedure is quite complicated.

Method 3: Take into Account the Most Prominent Issues

Here, we will discuss some steps that you must know on the basis of the configuration of the server.

  1. If you start with Cloudfare’s HTTPS, you might find that the parent server is not configured to permit Cloudfare’s IP address for accessing the port. But, if you can’t configure the firewall, then go for Flexible SSL in place of Full SSL present at the Cloudflare.
  2. Then, ensure that you are using only the latest version of Bad Behavior or the mod_security. This is possible only if applicable.
  3. If you find mod_antiloris or mod_reqtimeout Apache modules, then it’s time to deactivate and unload these modules.

 Now, you will easily be able to resolve Cloudflare error 521.

Final Verdict

Hopefully, this article helps you to fix the error message 521 instantly. Just go through this informative content once to get a good grasp of the troubleshooting steps.

If you enjoy this tutorial, feel free to provide your suggestions in the comment section.

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