• Origin server returns an empty, unknown, or unexpected response to Cloudflare


Step 1: Grey Cloud The DNS Record

The quick step is to either grey cloud the DNS record in the Cloudflare DNS app or temporarily pause Cloudflare

Step 2: Contact NET Support

Contact NET support or your site administrator and request a review of your origin web server error logs for crashes and to check for these common causes:

  • Origin web server application crashes
  • Cloudflare IPs not whitelisted at your origin web server.
  • Origin web server TCP idle timeouts shorter than 300 seconds
  • Headers exceeding 8 KB (typically due to too many cookies)
  • An empty response from the origin web server that lacks an HTTP status code or response body
  • Missing response headers or origin web server not returning proper HTTP error responses
Step 3: Contact Cloudflare Customer Support

If the error continues after contacting NET support or site administrator, provide the following information to Cloudflare Customer Support: –

  • Full URL(s) of the resource requested when the error occurred
  • Cloudflare cf-request-id or cf-ray from the 520 error message
  • Output from with your hostname and domain where the 520 error occurred)
  • Two HAR files: one with Cloudflare enabled on your website, and the other one with Cloudflare temporarily disabled.