“Error 521: Web server is down”
Cloudflare is working, but when it tried to fetch your page from your own server (the origin), the server refused the connection. Cloudflare then shows this page with your browser and Cloudflare marked as working and the host marked as the problem.
Is your site showing it right now?
The free scan loads your page like a visitor and checks for this message, plus broken links, script errors and phone layout. It also walks your signup, booking or contact form, without sending anything.
Free, no signup. Usually done in about a minute.Why it happens
- The web server on your origin is stopped or crashed
- A firewall or security plugin on the origin blocks Cloudflare's addresses
- Cloudflare's SSL mode doesn't match the origin: "Full" needs the origin to answer on port 443
How to fix it
Check the origin directly
Visit the origin's own address (from your host's panel, or by pointing your computer's hosts file at the origin IP). If it doesn't load there either, the web server is down: restart it or ask your host.
Allow Cloudflare's addresses
Cloudflare lists its IP ranges at cloudflare.com/ips. Make sure your server firewall, your host and any security plugin allow all of them; blocking even some causes 521s.
Match the SSL mode to the origin
In Cloudflare, SSL/TLS: with "Full" or "Full (strict)" the origin must accept HTTPS on port 443 (with a valid certificate for strict). If it only serves HTTP, use "Flexible" for now, then add a certificate on the origin.
Ask your host
If the origin looks fine, ask your host whether they rate-limit or block Cloudflare. Some do it to fight attacks.
Questions
What's the difference between 521 and 522?
521: the origin refused the connection. 522: the origin didn't answer in time. Both point to the origin server, not Cloudflare.
Can I just pause Cloudflare?
Pausing Cloudflare sends visitors straight to the origin, which helps you test, but if the origin is down the site stays down. Fix the origin first.
Can Page Canary tell me if this comes back?
Yes. Page Canary checks your key pages every day for this message and others like it, confirms it on a second check, and emails you with the fix. One site is free.