HTTP 520 Unknown Error — What It Means and When You See It
Quick Answer
HTTP 520 Unknown Error is a Cloudflare-specific status meaning the origin server returned an unexpected, empty, or non-HTTP response to Cloudflare.
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Frequently Asked Questions
Related Values
100
HTTP 100 Continue means the server has received the request headers and the client should proceed to send the request body. It is an interim response used to inform the client to continue.
101
HTTP 101 Switching Protocols indicates the server is switching to the protocol specified in the Upgrade header field. Commonly used when upgrading to WebSocket connections.
200
HTTP 200 OK is the standard success response. The request has succeeded and the server has returned the requested resource in the response body.
201
HTTP 201 Created means the request succeeded and a new resource was created as a result. The Location header typically points to the new resource URL.