HTTP 429 means the target or an edge service rate-limited the monitoring request. WebCheck reports the response as an unexpected status unless the target is deliberately configured to accept it.
Why it happens
- The monitor interval is too aggressive for the endpoint.
- A WAF or CDN groups monitoring traffic with other automated requests.
- A shared hosting or API quota has been reached.
- The target has a burst limit that is lower than the configured monitoring cadence.
How to investigate
Review response headers such as Retry-After, application rate-limit logs, CDN security events and the target interval. Compare 429 runs with normal runs and check whether several targets share the same limit.
Safer fixes
- Monitor a lightweight public health endpoint.
- Allow the monitoring request within the existing rate-limit policy where appropriate.
- Choose an interval permitted by your WebCheck plan and suitable for the service.
- Keep the target protected rather than removing rate limits globally.
Limitation
A 429 response is evidence that this request was limited. It does not identify by itself whether the application, CDN or WAF made the decision.