Uptime Basics treats HTTP 200-399 responses as healthy by default. You can also accept individual HTTP 400-599 responses when an error-class response is the correct, expected result for the endpoint you chose.
For example, a protected API endpoint may intentionally return HTTP 401 when it is reachable but no credentials are supplied. Adding 401 tells the monitor that this exact response confirms availability.
Add an accepted status code
When creating a monitor:
- Open New Monitor.
- Find Advanced request options.
- Enter one HTTP code in Additional accepted HTTP error codes.
- Press Enter. The code appears as a removable item.
- Repeat for any other intentional response, then create the monitor.
For an existing monitor, open Advanced Request Options on the monitor detail page, add or remove codes, and save the changes.
Only individual codes from 400 through 599 can be added in the customer interface. HTTP 200-399 responses remain accepted automatically and do not need to be entered.
Choose codes carefully
Accept a code only when it has a stable meaning for the exact URL being monitored. Common examples include:
- 401 for an endpoint that intentionally requires authentication;
- 403 for a reachable endpoint that intentionally denies this request;
- 404 for a deliberate health-check path whose expected response is Not Found.
Avoid accepting broad server failures such as 500, 502, 503, or 504 for a normal website. Doing so makes those responses count as Up, prevents them from contributing to an availability incident, and can hide a real outage.
What changes after a code is accepted
The check log still records the actual HTTP response. The accepted code changes the availability decision for that monitor:
- the check is recorded as Up;
- the response contributes to uptime as a successful check;
- an outage alert is not created solely because of that response.
This setting does not change the response returned by the monitored site and does not bypass authentication or access controls.
If a code is unexpected, remove it and investigate the endpoint instead. For help interpreting a response, open the matching troubleshooting guide or contact Uptime Basics support.