Cloudflare, reporting on the origin behind it.
Cloudflare error 520 — Web server returned an unknown error
Cloudflare reached the origin and got something it could not interpret — an empty reply, a reset connection, or headers that break the spec. It is Cloudflare's catch-all for "the origin misbehaved".
A proxy does not fix this. This is a failure between Cloudflare and the site's own server. Your address plays no part in it, and no pool will change the outcome.
Why it happens
The origin crashed or reset the connection mid-response.
Response headers too large — an oversized cookie set by the origin is a classic cause.
The origin is rejecting Cloudflare's request shape rather than yours.
How to fix it
- Retry: 520s are frequently transient.
- Try without the proxy. A 520 that reproduces direct is the site's problem and nothing you do will fix it.
- Trim your own cookie jar if a long session may have grown the request past a limit.
FAQ
What does 520 mean?›
Cloudflare reached the origin and got something it could not interpret — an empty reply, a reset connection, or headers that break the spec. It is Cloudflare's catch-all for "the origin misbehaved". Cloudflare, reporting on the origin behind it.
Why am I getting 520?›
The origin crashed or reset the connection mid-response. Response headers too large — an oversized cookie set by the origin is a classic cause. The origin is rejecting Cloudflare's request shape rather than yours.
How do I fix 520?›
Retry: 520s are frequently transient. Try without the proxy. A 520 that reproduces direct is the site's problem and nothing you do will fix it. Trim your own cookie jar if a long session may have grown the request past a limit.
Will a proxy fix 520?›
This is a failure between Cloudflare and the site's own server. Your address plays no part in it, and no pool will change the outcome.