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521 Error Cloudflare: How to Troubleshoot & Repair

Expert solutions to open the otherwise inaccessible website

5 min. read

Updated onNovember 8, 2023

updated onNovember 8, 2023

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Cloudflare is a popular name amongst those who understand the backend of the Internet and the aspects concerning security and privacy. Its primary role is to make things faster, more secure, and more reliable. But, the Cloudflare 521 error acts as an impediment when accessing a website.

The message reads,Web server is down, Error code 521,and is usually encountered onwebsites developed using WordPress. The problem has been present for a long time and gives developers and users a hard time. So, let’s find out all about it!

What is Cloudflare error reference number 521?

The error appears when the server doesn’t respond to requests from Cloudflare. And while the message lists server issues as the reason behind the errors, that’s not always the case.

Here are a few reasons users encounter the 521 error in Cloudflare:

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How do I fix 521 error Cloudflare?

Before we move to the slightly complex solutions, here are a few quick things to try:

If none work, head to the fixes listed next.

1. Check the site status

For those wondering how to fix Cloudflare errors, your primary approach should be ensuring the site’s running fine. The easiest option is to run apingtest via the command line.

Use the following command for it while replacingwebsitewith the actual address:ping website

For instance, when checking for issues with theWindowsReport, the command becomes as follows:ping windowsreport.com

Check the test results and look for any anomalies here. Besides, you could useDowndetector, a reliable service that allows users to report issues with the website, thus providing statistics in real time.

2. Whitelist for Cloudflare

When the website’s status is fine, the next possible reason for the 521 error Cloudflare with DigitalOcean is blocking connection attempts at the backend. In this case, you must ensure that Cloudflare IPs are not blocked in the firewall,.htaccess, andiptables.

You can use the following command to allow connections from a given IP iniptableswhile replacingIP Addresswith the one for Cloudflare:sudo iptables -A INPUT -s IP Address –dport 443 -j ACCEPT

Check thefull list of Cloudflare IPs, whitelist all these, and make sure port 443 is accessible. The process might be slightly different for each, depending on the configured firewall, but it shouldn’t be too tricky.

Also, while verifying this aspect, make sure to check with the hosting service whether they are blocking connection attempts from Cloudflare, and get this rectified,

3. Check for issues with the SSL certificate

For many users getting the 521 error Cloudflare with WordPress, the problem lies with the website’s security certificates. Users can generate the certificate from Cloudflare’s dashboard and upload it to the web server to eliminate such issues and ensure seamless connectivity.

In case the website already has an SSL certificate, check for issues with it and make sure the other settings are configured right.

4. Reconfigure the encryption settings

Often, an incorrect encryption mode can trigger a 521 error Cloudflare with Nginx. Cloudflare offers several modes designed per the website’s and developer’s requirements. These are:

Now that you understand the three switch to different modes and verify which works best for your website, though it’s usuallyFlexible. Again, it depends on several factors, and for some users, setting SSL mode toFull (strict)did the trick.

5. Contact support

If none of the solutions listed here helped fix CloudflareError code 521, the last option is tocontact Cloudflare support. They can better assist you if the underlying cause is tricky to identify.

Once things are up and running, get areliable network and traffic inspection toolfor detailed insights. In case you’re dealing with additional issues, don’t miss ourCloudflare error 1001 guide.

For any queries or to share the solution that worked for you, drop a comment below.

521 Error Cloudflare: How to Troubleshoot & Repair#

How do I fix 521 error Cloudflare?#

1. Check the site status#

2. Whitelist for Cloudflare#

3. Check for issues with the SSL certificate#

4. Reconfigure the encryption settings#

5. Contact support#