All our servers are currently hosted on Amazon AWS eu-west-1 in Ireland. Below is a list of the IPs Hotjar uses to send egress, outgoing, traffic from which you can whitelist if required on your end.
18.203.61.76
18.203.176.135
52.17.197.221
Note
The IPs listed above do not cover the actual domain https://insights.hotjar.com. This is due to it being served by our CDN provider. We suggest to whitelist the domains *.hotjar.com.