Core networking

mask.icloud.com

mask.icloud.com and mask-h2.icloud.com are the iCloud Private Relay hosts. With Private Relay on, Safari browsing and DNS lookups travel through them to Apple's ingress proxy.

Run by ApplePorts: 443 UDP (mask), 443 TCP (mask-h2)Checked: 1 November 2026

Short answer

The iCloud Private Relay hosts. With Private Relay on, Safari browsing and DNS lookups go through them.

Block with care

Blocking them stops iCloud Private Relay on that network. Turning off Limit IP address tracking for that network does the same thing cleanly.

Matches
mask.icloud.com mask-h2.icloud.com

A name with *. covers every name under it: *.push.apple.com matches 1-courier.push.apple.com.

What it serves

Apple's enterprise host list names mask.icloud.com on UDP 443 and mask-h2.icloud.com on TCP 443, both for iCloud Private Relay.

Apple Platform Security says that Private Relay uses two proxies, an ingress run by Apple and an egress run by a content provider. No single party, not even Apple, can link your IP address and your browsing.

Apple's port list names UDP 443, QUIC, for iCloud Private Relay. On a Mac, networkserviceproxy carries this traffic.

Processes that use it

networkserviceproxyPart of macOS. It is the transparent proxy for Apple system services and can carry iCloud Private Relay traffic, so other apps' browsing can show under it.Process →

What breaks if you block it

Block with care

Blocking them stops iCloud Private Relay on that network. Turning off Limit IP address tracking for that network does the same thing cleanly.

What breaks if you block it

  • iCloud Private Relay can't connect, so it stops hiding your IP address from websites on that network.
  • Browsing and DNS lookups then go out directly, without the relay's protection.

With Kilobat Pro and the network filter, you can block a host for every app or for one app: in Connections, select a connection and choose Block. Apple’s own services are never blocked by Kilobat’s Protection lists.

Notes

To turn off Private Relay for one network, open that network's Details and turn off Limit IP address tracking. See Limit IP address tracking on a Mac.

Apple’s rules for its hosts

Apple’s list, Use Apple products on enterprise networks, says that devices open these connections, not Apple’s servers. Apple services fail any connection that uses HTTPS interception, so a proxy that inspects TLS should leave Apple’s hosts alone.

If a firewall allows hosts by name, allowing *.apple.com covers most Apple services, Apple says. A firewall that works only with addresses can allow 17.0.0.0/8 for IPv4, and 2403:300::/32, 2620:149::/32 and 2a01:b740::/32 for IPv6.

To see which app on your Mac opened a connection to this host, use Kilobat’s Connections tab, or the agent network log for AI agents.

Sources

Checked on 1 November 2026.