Probe Servers and Whitelisting for Firewalls (List of Probe Server IPs)

For’s probe servers to communicate successfully with your web resources, it may be necessary to whitelist our probe servers. This ensures connectivity if, for example, your organization operates a firewall that prevents outside connections. If you are seeing checks fail (usually with a “403 Forbidden” result) and suspect that the issue is not due to the resource being truly down, we suggest working with your IT department to whitelist our probe servers. A full list of probe servers can be found by navigating to Support > Public Probe Servers, or by clicking this link while logged into your account.

Please note: you will not necessarily need to whitelist every probe server. However, please make sure that you whitelist ALL of the servers in the specific Locations you intend to use on your checks. We recommend your team be aware of the locations you have chosen to avoid false positives. 

When whitelisting probe servers, we also highly recommend using the “Subscribe to Updates” feature on this page. You will receive notifications about any new or changed servers so they can be whitelisted as they are available. We are continuously expanding our coverage with new regions represented—as well as adding to our server list in already-covered regions—to ensure the best possible results in your monitoring.


For more information about Probe Servers, please see the related documentation located here.

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