Error 521
Error 521 Web Server Is Down Error
What This Error Means
This is a Cloudflare-specific error indicating that the origin web server refused the connection from Cloudflare.
Common Causes
- Origin server is down.
- Firewall on the origin server blocking Cloudflare IPs.
- Web server software (Apache/Nginx) is not running.
- Port 80 or 443 is closed.
How to Fix It (For Users)
- 1 Wait for the site owner to fix the issue.
- 2 View a cached version if available.
For Site Owners / Developers
- Ensure the web server is running.
- Whitelist Cloudflare IP ranges in your firewall.
- Check server logs for errors.
- Verify port 80/443 availability.
When It Is NOT Your Fault
If the website's hosting provider is down.
Check if this outage affects everyone globally
This error often indicates a wider problem. Use our tool to verify if the site is down for everyone.
Check Website Status →Recommended Tool to Prevent This Error
Fix DNS resolution issues and protect your site from DDoS attacks with Cloudflare.