Error 520: web server returns an unknown error

I am getting 520 error vary frequently after activating CDN. here is few info - Ray ID: 6cd4edf119ac7dac … Let me know if there is any solution, else I have to deactivate cloudflair.

Please click on the 520 link in your post.

3 Likes

Not necessarily, you should try the following first

  1. Your web server or networking equipment, any http aware device like Firewall, Load Balancer, et al, reset the TCP connection after it was established. Sometimes when a web server crashes it will reset the connection. Check your web server error logs with your hosting provider for the time that the error occurred to see any error messages.
  2. Your web server returned an invalid response that exceeded our limits. Often this can happen if your web server is returning too many/too large headers. This is often caused by runaway scripts that return too many cookies, for example. The Code Igniter PHP framework has some known bugs around this, too.
  3. While you’re having a conversation with your hosting provider, make sure they include Cloudflare IPs on their allowed list.
  4. While the 520 error can be triggered by unique and seemingly strange edge-case scenarios, they are generally caused by: Connection resets (following a successful TCP handshake), Headers exceed the Cloudflare header size limit (over 8kb), An empty response from origin, An invalid HTTP response, Missing response headers from an HTTP response, or the Presence of multiple Content-Length headers.
  5. Note that if Always Online is enabled, this error will trigger an Always Online page to be served. Disable Always Online and check to see if the error goes away or changes. If so, consult the appropriate 521 or 522 #CommunityTip.
  6. If this error is still happening, post on this site and provide example URL(s) and Ray ID and output from a traceroute from any impacted user, copy the output of example.com/cdn-cgi/trace - replace example.com with the affect domain. Also prepare two HAR file(s) : one detailing your request with Cloudflare enabled on your website and the other with Cloudflare temporarily disabled - see How do I temporarily deactivate Cloudflare ? If Cloudflare Support needs to assist, these HAR files will be helpful in comparing server responses.

This topic was automatically closed 15 days after the last reply. New replies are no longer allowed.