How to use it
- Enter the address and read the status code from the live check.
- Find the code in the table below.
- Follow the advice for visitors, or the one for site owners.
How status codes are grouped
The first digit tells you who owns the problem. Codes starting with 2 mean success. Codes starting with 3 are redirects. Codes starting with 4 are errors the server blames on the request, and codes starting with 5 are errors on the server. For the question "is the site down?" the line between 4 and 5 is the one that matters: a 4xx page still proves a server is running.
The meanings below follow the MDN HTTP status reference and the Cloudflare error documentation, checked on 25 October 2026.
Client errors: 4xx
| Code | Name | Meaning | Site down? |
|---|---|---|---|
| 400 | Bad Request | The server could not process the request, for example because of malformed syntax or an oversized cookie. | No. Delete cookies for the site. |
| 401 | Unauthorized | You must sign in to get this page. | No. |
| 403 | Forbidden | The server knows who you are, or what you are, and refuses access. | No. Try without a VPN. |
| 404 | Not Found | Nothing exists at this address. | No. Check the link. |
| 405 | Method Not Allowed | The address exists but does not accept this kind of request. | No. |
| 408 | Request Timeout | The server closed an idle connection. | No. Reload. |
| 410 | Gone | The content was permanently deleted. | No. |
| 429 | Too Many Requests | You hit the rate limit. | No. Wait a few minutes. |
Server errors: 5xx
| Code | Name | Meaning | Site down? |
|---|---|---|---|
| 500 | Internal Server Error | The server hit a situation it could not handle and no more specific code fits. | Yes, or broken. |
| 502 | Bad Gateway | A gateway or proxy got an invalid response from the server behind it. | Yes. |
| 503 | Service Unavailable | The server is not ready to handle the request, usually from maintenance or overload. | Yes. |
| 504 | Gateway Timeout | A gateway did not get an answer in time. | Yes. |
Cloudflare errors 520 to 530
A large share of sites sit behind Cloudflare, which acts as a gateway between visitors and the site's own server. When Cloudflare cannot get a proper answer, it shows its own page with a code in the 52x range. According to Cloudflare, these are the common ones:
| Code | Cloudflare's description | In plain words |
|---|---|---|
| 520 | Web server returns an unknown error | The server sent something Cloudflare did not understand. |
| 521 | Web server is down | The server refused the connection or is switched off. |
| 522 | Connection timed out | The server did not answer the connection attempt in time. |
| 523 | Origin is unreachable | Cloudflare has no working route to the server. |
| 524 | A timeout occurred | The server connected but took too long to reply. |
| 525 | SSL handshake failed | The secure connection to the server could not be set up. |
| 526 | Invalid SSL certificate | The server's certificate is not valid. |
In every case the fault is between Cloudflare and the site's own server, so visitors cannot fix it. If you run the site, restart the web server, check that its firewall allows Cloudflare and look at its certificate settings.
What you can do as a visitor
For a 4xx code, change something on your side: fix the link, sign in, switch off the VPN or slow down. For a 5xx code, wait. Reload after a minute or two, because many 502 and 503 pages come from a short restart or a traffic spike. Avoid hammering the reload key. Each extra request adds load to a server that is already struggling, and a rate limit can turn your 503 into a 429.
What you can do as the site owner
Start with the error log of the web server and the application, then the change you made last. A 500 right after a deploy usually means the deploy. A 502 or 504 behind a reverse proxy often means the application process crashed or is too slow, so look at memory and worker limits. A 503 during traffic peaks means the server needs more capacity or a cache in front. After the fix, confirm from the outside with the website down checker, because your own browser may still show a cached error.
Related
If you see a browser message instead of a number, such as a timeout or a name resolution error, read why a website is not loading. For manual tests, see how to check if a website is down.
Frequently asked questions
What is the difference between 502, 503 and 504?
502 means a gateway got an invalid answer from the server behind it. 503 means the server is unavailable, usually from overload or maintenance. 504 means the gateway waited for the server and gave up. All three are problems on the site's side.
Does a 403 mean the site is down?
No. The server is running and it understood the request, but it refuses to serve you. That can be a blocked region, a blocked address, a missing permission or a bot filter.
What does a 404 mean?
The server works, but it has nothing at that address. The link may be mistyped, old or removed. A site-wide 404 on pages that used to work usually means a broken deploy, not a down server.
Can I fix a 500 error myself?
As a visitor, no. Reload once, wait a few minutes and try again. If you own the site, check the server error log, the last change you made and your hosting status page.
What does error 429 mean?
Too many requests. You, or your network, sent more requests than the site allows in a given time. Wait a few minutes. If you share an address with many people, for example on a VPN, the limit may be hit by others.
What are Cloudflare errors 520 to 526?
They appear when a site uses Cloudflare and Cloudflare cannot get a proper answer from the site's own server. They are caused by the site, not by Cloudflare, in most cases. Visitors can only wait.