How to use it
- Type the site in Website or URL, either a name like
youtube.comor a full link, and press Check. - Read the verdict, then Status, Response time, Final address, Redirects and Checked from.
- If the site won't load for you, press Yes, it's down for me under Is it down for you too? The bars show the reports of the last 24 hours, hour by hour.
- Press Check again a minute later to see whether it has recovered: results are cached for one minute.
How the verdict is decided
The check sends one normal GET request from the Cloudflare data centre named in the result, follows up to 10 redirects and waits at most 8 seconds for each answer. The verdict comes from the last answer:
| What came back | Verdict |
|---|---|
| 200 OK or any other answer below 400 | is up |
| 403 Forbidden or 429 Too many requests | is up: the server runs but refuses automated checks |
| 404, 410 and other 4xx codes | answers, but with a problem |
| 503 Service unavailable | answers, but with a problem: RFC 9110 calls it a temporary overload or maintenance |
| 500, 502, 504 and Cloudflare's 520 to 526 | looks down |
| No answer in 8 seconds, DNS failure, TLS failure, connection refused | looks down |
| A redirect loop or more than 10 redirects | answers, but with a problem |
Cloudflare errors 520 to 526
Many sites sit behind Cloudflare. A 52x code means Cloudflare's edge answered but couldn't get a proper reply from the site's own server, the origin. Per Cloudflare's documentation:
- 520: the origin sent an empty, unknown or unexpected response.
- 521: the origin refused the connection.
- 522: Cloudflare timed out contacting the origin: no reply to its connection attempt within 19 seconds, or no acknowledgement of the request within 90.
- 523: no network route to the origin.
- 524: connected, but no HTTP response within 125 seconds (the default).
- 525: the TLS handshake with the origin failed.
- 526: the origin's certificate couldn't be validated.
Because this check gives up after 8 seconds, a site heading for a 522 or 524 shows up here as a timeout first.
Up here but not for you?
- Compare the address your device gets with the /dns-lookup: a stale DNS cache or a filtering resolver can send you to the wrong place.
- Try another network, such as mobile data instead of Wi-Fi. If that works, the problem is between you and the site.
- Turn off browser extensions, a VPN or a firewall for a moment.
- The check runs from one data centre. A regional outage elsewhere won't show, and an app can fail while its website still answers.
About the down reports
A report is a count, not a verified fact: what you see is how many visitors pressed the button in each hour. We store only the site name, the hour and the count, with no IP address, cookie or ID, and delete counts older than 30 days. One browser can report each site once per hour. A few reports can mean a local ISP problem; many in the same hour are a stronger sign of a wider outage. The service's own status page remains the best confirmation.
Questions
- Why does it say a site is up when it won't load for me?
- Our server reached it, so the fault is likely closer to you: your DNS, your ISP, your network or your browser. The tips above and the /dns-lookup help narrow it down.
- Why does a site that blocks the check count as up?
- A 403 or 429 is an answer from a running server. It only means the site refuses automated requests, which is common behind bot protection.
- What does the response time measure?
- The time from our request until the site's response headers arrive, added up over all redirects. It isn't the full page load in your browser, which also downloads images and scripts.
- Which data centre runs the check?
- The Cloudflare location that handled your request, shown in Checked from. Results from a different place can differ.
- Can I check a local server or a custom port?
- No. Only public addresses on ports 80, 443, 8080 and 8443 are checked, and addresses inside private networks are refused. To test a port on your own connection, use the /port-checker.