520 Web Server Returns an Unknown Error
The origin server sent Cloudflare an empty, unknown or unexpected response.
What to do
The origin sent Cloudflare an empty, unknown or malformed response. Check the origin's error log. A crash part way through a response, or very large headers, are common causes.
- Class
- 5xx Server Error. The server failed to fulfill a request that looked valid.
- Registered
- No. Cloudflare sends it, and it is not in the IANA registry, so other servers may mean something else by it.
- References
- Cloudflare
Every 5xx code
- 500 Internal Server Error
- 501 Not Implemented
- 502 Bad Gateway
- 503 Service Unavailable
- 504 Gateway Timeout
- 505 HTTP Version Not Supported
- 506 Variant Also Negotiates
- 507 Insufficient Storage
- 508 Loop Detected
- 510 Not Extended
- 511 Network Authentication Required
- 520 Web Server Returns an Unknown Error
- 521 Web Server Is Down
- 522 Connection Timed Out
- 523 Origin Is Unreachable
- 524 A Timeout Occurred
- 525 SSL Handshake Failed
- 526 Invalid SSL Certificate
- 530 (No name)
- 561 Unauthorized