What it means
520 isn't a standard HTTP code but Cloudflare's catch-all error. Cloudflare reached the origin server, but the response was unusable: the connection was reset, the response was empty or the headers were invalid.
Most common causes
- The origin server crashed or reset the connection mid-response.
- Response headers too large (e.g. too many Set-Cookie headers, over 128 KB).
- A firewall on the origin blocking Cloudflare's IPs.
- An empty response caused by an application error.
What you can do as a visitor
- Refresh the page after a few minutes.
- The site owner has to fix the error.
What the site owner or developer should do
- Check the origin server logs at the time of the error (use the Ray ID on the error page).
- Allow Cloudflare's IPs in your firewall and security plugins.
- Reduce the size of headers and cookies.
- Temporarily pause Cloudflare and check whether the origin works directly.
Impact on SEO and Google
As with other 5xx errors: brief outages do no harm, but prolonged ones slow crawling and put your indexing at risk.
Frequently asked questions
Is a 520 Cloudflare's fault?
Usually not. Cloudflare is reporting that the origin server didn't return a valid response.
Where do I find the Ray ID?
At the bottom of the error page. Use it when searching logs or contacting support.