When you run a check on UpChecker, the verdict line always shows a three-digit HTTP status code (or no code at all). Here is what each family means when the question is “is the site up?”.
200 is the normal answer. 301/302 (redirections) are also fine: the server is talking; it just points elsewhere. UpChecker counts anything below 400 as UP.
A redirect chain that ends nowhere can still mean a broken site for visitors even though every hop answers. If you see 301 constantly, check where the final landing page is.
| Code | Meaning for uptime |
|---|---|
| 403 | The server is alive but refused our plain GET request — usually a firewall or bot protection, not an outage. Real browsers may still load it fine. |
| 429 | Rate limiting. Same story: site is up, we asked too often. Wait before re-checking. |
| 404 | That exact URL doesn’t exist, but the site itself is answering — check the homepage instead. |
500 means the server crashed processing the request. 502 means a gateway got a bad response from the upstream server. 503 means the service is temporarily unavailable — often overloaded or mid-restart. 504 means a gateway timed out waiting for the upstream. Any of these is a genuine signal the site is struggling; users experience them as “the site is down”.
500 internal error, 502 bad gateway, 503 service unavailable (often overload or planned maintenance), 504 gateway timeout. The machine is talking but the application is failing — users experience this as “the site is down” even though cables are fine.
Timeouts, DNS failures, and refused connections produce no HTTP status. This is the only unambiguous “DOWN”: nothing answered. Causes range from expired domain and DNS outage to a crashed server or country-level blocking.
Run your own check on the UpChecker homepage — it’s free, no signup.