mullvad dns default hostname

When using mullvad vpn, which one of the following hostnames does it use by default, and can it be changed?

Each hostname has its own filtering so its easy to understand when using mullvad dns as custom dns on devices without a vpn, but if using the vpn i want to know which filtering does it use and if it can be modified.

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You can change it in the Mullvad VPN app by going on the gear on the top right →VPN settingsDNS content blockers. There you can select what to use. Using the Mullvad VPN app