Error Code Portal
CloudflareCloudflare HTTP errorsError code

520

Error 520: web server returns an unknown error

Alternative forms: Error 520

What does this code mean?

Code 520 · An issue reported by Cloudflare HTTP errors.

Official explanation · Original text

This error occurs when the origin server returns an empty, unknown, or unexpected response to Cloudflare. This error is often triggered by:

Troubleshooting and diagnostic links

First check that the document's product, version, and environment match your situation.

Source and terms of use

Error 520: web server returns an unknown error ↗

Creator: Cloudflare, Inc. and contributors
License: Creative Commons Attribution 4.0 International
Checked on: 2026-11-12

Modifications: Selected introductory official description; Markdown stripped; original Korean product context added. Direct official error page retains the complete cause and resolution instructions.

Source details · Original licenses and notices