HTTP status code 521 (Web Server Is Down) means: The website's server refused the connection from Cloudflare (the web server is down or blocking Cloudflare). Yes, a server error: the website failed to handle the request. Usually only the site owner or host can fix it.
Is it an error?
Yes, a server error: the website failed to handle the request. Usually only the site owner or host can fix it.
Common causes
- Web server offline or refusing connections
- Firewall or security plugin blocking the proxy/CDN's IP addresses
If you are visiting the site
- Wait a few minutes before trying again
- Contact the website if the problem continues
If you run the website
- Allow Cloudflare's IP ranges in the server firewall and security plugins
- Make sure the backend (e.g. PHP-FPM or app server) is running and responding
- Check the SSL/TLS mode: Full (strict) requires a valid, trusted certificate
- Ask your hosting provider to check the server
Frequently asked questions
What does HTTP 521 mean?
HTTP status code 521 (Web Server Is Down) means: The website's server refused the connection from Cloudflare (the web server is down or blocking Cloudflare).
Is HTTP 521 an error?
Yes, a server error: the website failed to handle the request. Usually only the site owner or host can fix it.
How do I fix a 521 error?
If you are visiting the site: Wait a few minutes before trying again; Contact the website if the problem continues. If you run the website: Allow Cloudflare's IP ranges in the server firewall and security plugins; Make sure the backend (e.g. PHP-FPM or app server) is running and responding; Check the SSL/TLS mode: Full (strict) requires a valid, trusted certificate; Ask your hosting provider to check the server.