--- title: "mask.icloud.com: what it is and what breaks if you block it · Kilobat" url: "https://kilobat.app/hosts/mask-icloud-com" description: "mask.icloud.com and mask-h2.icloud.com carry iCloud Private Relay traffic. What happens when a network blocks them, and how to skip the relay." --- 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 Apple · Ports: 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`](https://kilobat.app/processes/networkserviceproxy) carries this traffic. ## Processes that use it - [networkserviceproxy](https://kilobat.app/processes/networkserviceproxy): Part 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. ## 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](https://kilobat.app/docs/blocking#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](https://kilobat.app/guides/limit-ip-address-tracking). ## Apple’s rules for its hosts Apple’s list, [Use Apple products on enterprise networks](https://support.apple.com/en-us/101555), 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](https://kilobat.app/docs/agents#agent-network-log) for AI agents. ## Sources - [Apple Support: Use Apple products on enterprise networks](https://support.apple.com/en-us/101555) - [Apple Platform Security: iCloud Private Relay security](https://support.apple.com/guide/security/icloud-private-relay-security-secad8ce3233/web) - [Apple Support: About iCloud Private Relay](https://support.apple.com/en-us/102602) - [Apple Support: TCP and UDP ports used by Apple software products](https://support.apple.com/en-us/103229) Checked on 1 November 2026. ## Related - [mask-api.icloud.com](https://kilobat.app/hosts/mask-api-icloud-com): An iCloud Private Relay host on TCP 443. Unlike the relay hosts, Apple says that it supports proxies. - [doh.dns.apple.com](https://kilobat.app/hosts/doh-dns-apple-com): Apple's DNS over HTTPS (DoH) host. Apple lists it for encrypted DNS resolution in macOS Big Sur and later. - [iCloud Private Relay breaks some websites](https://kilobat.app/guides/icloud-private-relay-sites) - [Limit IP address tracking on a Mac](https://kilobat.app/guides/limit-ip-address-tracking)