Downtime root causes – Unexpected Status Code

This article will take you through the reasons for a “Unexpected status code” root cause on an uptime test.

We return this error type when we see an unexpected status code returned by the tested website, this can be any common error status code, or a custom status code depending on what you have chosen to include in the “Status Codes” section of test settings.

Some common status codes that will by default give an error are:

  • 400 – The target server refuses to process the request due to a perceived issue with the data being sent
  • 403 – Access to the server is forbidden
  • 404 – The requested page or file was not found on the server
  • 405 – The method is not allowed, for example you are connecting by POST when the server only accepts GET
  • 429 – This is a sign that too many requests have been sent to the target server, and is a common method of rate limiting
  • 500 – This indicates an internal server error, the target server does not know how to handle the error
  • 503 – The target server is unavailable, and unable to handle the request. Common causes include the server being down for maintenance, or overloaded

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