{"id":7227,"date":"2026-07-19T09:55:27","date_gmt":"2026-07-19T09:55:27","guid":{"rendered":"https:\/\/checksitestatus.com\/?p=7227"},"modified":"2026-07-19T09:59:14","modified_gmt":"2026-07-19T09:59:14","slug":"521-522-523-cloudflare-error","status":"publish","type":"post","link":"https:\/\/checksitestatus.com\/fr\/521-522-523-cloudflare-error\/","title":{"rendered":"521\/522\/523 Cloudflare Error: What It Means and How to Fix It"},"content":{"rendered":"\t\t
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If you’re running a site behind Cloudflare and a visitor suddenly sees an orange error screen with a number like 521, 522, or 523, the problem isn’t Cloudflare itself. It’s almost always your origin server, the actual machine hosting your website, that Cloudflare can’t reach.

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These three codes look similar and get mixed up constantly, but they point to different failures. Getting the right one narrowed down saves a lot of time, because the fix for “my server crashed” is completely different from “my DNS record points at the wrong IP.”

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Why these errors exist in the first place<\/strong><\/h2>

Cloudflare sits between your visitors and your actual web server, acting as a reverse proxy. When someone requests your site, Cloudflare’s edge network handles the request first, then forwards it to your origin server if needed and passes the response back. That middle position is what makes Cloudflare fast and gives it DDoS protection, but it also means there’s a whole extra hop that can fail.

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Codes in the 520 to 526 range are Cloudflare-specific. They don’t exist in the standard HTTP specification; they’re Cloudflare’s own way of telling you specifically where in that middle hop things broke down, instead of just returning a generic 502 or 504 the way an ordinary proxy would.<\/p>

Code<\/th>Name<\/th>Quick meaning<\/th><\/tr><\/thead>
520<\/td>Web Server Returned an Unknown Error<\/td>The origin sent back something Cloudflare couldn’t parse.<\/td><\/tr>
521<\/td>Web Server Is Down<\/td>Cloudflare couldn’t establish a connection to the origin at all.<\/td><\/tr>
522<\/td>Connection Timed Out<\/td>Cloudflare connected but got no response before timing out.<\/td><\/tr>
523<\/td>Origin Is Unreachable<\/td>Cloudflare can’t route to the origin’s IP address.<\/td><\/tr>
524<\/td>A Timeout Occurred<\/td>The origin accepted the connection but took too long to send data back.<\/td><\/tr>
525<\/td>SSL Handshake Failed<\/td>Cloudflare and the origin couldn’t agree on an SSL\/TLS connection.<\/td><\/tr>
526<\/td>Invalid SSL Certificate<\/td>The origin’s SSL certificate is invalid, expired, or self-signed in a way Cloudflare rejects.<\/td><\/tr><\/tbody><\/table><\/div>

The rest of this guide focuses on 521, 522, and 523, since they’re the three that come up most often and cause the most confusion.

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521: Web Server Is Down<\/strong><\/h2>

This means Cloudflare tried to open a TCP connection to your origin server on the port it expects (usually 80 or 443), and the server refused it or never responded to the connection attempt at all. Cloudflare can reach your network; it just can’t get your web server to pick up.

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Common causes:<\/strong><\/p>