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HTTP Sensor "fooled" by error page



Good afternoon,

Some of the sites I cover with HTTP sensors automatically put up an error page when the sites aren't available. However, this fools the HTTP sensors into believing that the site is up and thus fails to trigger the fail status and subsequent alert.

Any idea on how this could be avoided?


detection http sensor

Created on Apr 20, 2021 3:17:17 PM

1 Reply




Thank you for your message.

Can you please provide us the URL from one of the websites so we can have a look on our side. When the website is not available, can you please check the HTTP response status code returned by the web server.

If the code belongs to the range 2xx, then the HTTP is working as expected as indicated in this kb article: https://kb.paessler.com/en/topic/65731-which-http-status-code-leads-to-which-http-sensor-status

Depending on the error page you get, you could use a custom script (examples available here) with an EXE/Script or EXE/Script Advanced sensor, which will take the error page into account independently of the response code.

If you have questions, let us know.


Created on Apr 21, 2021 11:47:53 AM by  Florian Lesage [Paessler Support]

Disclaimer: The information in the Paessler Knowledge Base comes without warranty of any kind. Use at your own risk. Before applying any instructions please exercise proper system administrator housekeeping. You must make sure that a proper backup of all your data is available.