Cloudflare error: what it means and how to fix it

Also searched as: cloudflare not working

Updated 11 October 2026

Short answer

Cloudflare sits in front of your website. Visitors connect to Cloudflare, and Cloudflare fetches the page from your own server (called the "origin"). When you see a Cloudflare error page, it's usually Cloudflare telling you it couldn't get a good answer from your server. So the fix is usually on your server or with your host, not in Cloudflare. The error number tells you exactly which step failed.

What's the problem

Visitors see a Cloudflare-branded page with an error number, a "Ray ID", and a diagram showing your browser, Cloudflare and your host, with one of them marked as the problem.

Why it happens

The number is the clue:

  • 520: your server sent back something empty or unexpected.
  • 521: your server refused the connection: it's down, or blocking Cloudflare.
  • 522: your server didn't answer in time: it's overloaded, offline, or a firewall is dropping Cloudflare.
  • 523: Cloudflare can't reach your server's address at all, usually a wrong IP in DNS.
  • 524: your server accepted the request but took too long to finish it.
  • 502 or 504: your server itself returned a bad gateway or timeout error.
  • 1000-series errors (1016, 1020 and others) are about Cloudflare settings: DNS, firewall rules or access.

How to fix it

  1. Note the error number and the Ray ID on the page. See Cloudflare Ray ID.
  2. Look at the diagram. If it marks "Host" as the error, the problem is your server.
  3. Check your server is running and reachable at the IP address in your Cloudflare DNS records.
  4. Check your server isn't blocking Cloudflare. Firewalls and security plugins sometimes block Cloudflare's IP addresses.
  5. Check Cloudflare's status page to rule out a Cloudflare incident.
  6. Contact your host with the error number, Ray ID and time, as Cloudflare's own guidance recommends.

What Preventionlabs checks

One click runs the full report on your domain. For this problem it shows whether your site loads, how fast, and where its redirects go; uptime checked every 5 minutes, with an email when the site goes down and when it is back. With Cloudflare connected, it also shows which pages returned server errors (5xx) to visitors, and when; your SSL mode and the other settings that commonly cause this; which requests the firewall blocked, by Cloudflare's own rule names; recent deploys and account changes, with their times; DNS changes in the last 7 days.

Run your free report

Your first report is free, no card needed. Then A$50 a month, up to 10 domains. Read-only: it never changes anything.

Sources

  1. Cloudflare: Cloudflare 5xx errorsofficial docsWhen troubleshooting most 5XX errors, the correct course of action is to first contact your hosting provider or site administrator to troubleshoot and gather data.

Related

Cloudflare error 522: connection timed out Error 522: Cloudflare couldn't connect to your server in time. The server is overloaded or offline, or a firewall is silently dropping Cloudflare. Cloudflare error 521: web server is down Error 521: your server refused Cloudflare's connection. The web server is stopped or a firewall is blocking Cloudflare. Start it, allow Cloudflare. Cloudflare error 520 Error 520: your server sent Cloudflare an empty or unexpected response. Usually a crash, a security plugin blocking Cloudflare, or response headers too large. Cloudflare Ray ID error The Ray ID isn't the error. It's a reference number for the request that failed. Use it with the error code to find that exact request in Cloudflare.

Preventionlabs is independent and not affiliated with Cloudflare. Product names are used only to describe the problem.

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