Here’s how to fix Error 521 with WordPress and Cloudflare. Error 521 can be exasperating, interrupting your WordPress site’s accessibility through Cloudflare.

Fear not!

We’ll delve into an array of comprehensive solutions to rectify this issue, ensuring your site is back online and functioning seamlessly.

Error 521 with WordPress and Cloudflare

Understanding Error 521

When visiting your WordPress site via Cloudflare and encountering Error 521, it’s crucial to comprehend its root cause before diving into resolutions. This error occurs when the web server refuses the connection initiated by Cloudflare, leaving the user unable to access the site.

Step 1: Verify Server Availability

The initial step involves confirming the availability and functionality of your WordPress site’s server. Execute the following steps:

  1. Linux/Mac Users: Utilize the cURL command in Terminal to check server status.
  2. Windows Users: Leverage KeyCDN’s HTTP Header Check tool, inserting your server’s IP address.

The expected outcomes:

  • A successful connection: HTTP 200.
  • Issues: Messages like Host Not Found or Failed to Connect indicate server problems.

If your server appears to be down, promptly seek assistance from your hosting provider’s support team.

Step 2: Whitelist Cloudflare IP Ranges

Even if your server seems functional, if Error 521 persists, consider whitelisting all Cloudflare IP ranges to ensure they aren’t blocked:

  1. Access the Cloudflare IP ranges list and ensure no IP addresses are restricted in .htaccess, iptables, or your firewall settings.
  2. Ensure your hosting provider doesn’t restrict or block IP requests from Cloudflare.

Should uncertainty persist about this process, seek guidance from your hosting support team. In most cases, Cloudflare IP ranges are pre-whitelisted for Pressillion users.

Step 3: Troubleshoot Specific Configurations

For a more nuanced approach, explore specific configurations based on your server setup:

  1. HTTPS Configuration: Verify whether your origin server permits Cloudflare’s IP addresses to access port 443. If restricted, consider switching to Flexible SSL instead of Full SSL within Cloudflare.
  2. Software Updates: Ensure you’re using the latest versions of Bad Behavior or mod_security, if applicable.
  3. Apache Modules: If utilizing mod_antiloris or mod_reqtimeout, experiment by disabling and unloading these modules.

Taking these technical steps might resolve the Error 521 encountered while using Cloudflare with your WordPress site.


Resolving Error 521 requires a multi-faceted approach, ensuring your WordPress site functions flawlessly with Cloudflare’s services. Implementing these solutions meticulously can help restore accessibility to your website.