---
title: "mask-api.icloud.com: what it is and what breaks if you block it · Kilobat"
url: "https://kilobat.app/hosts/mask-api-icloud-com"
description: "mask-api.icloud.com is an iCloud Private Relay host that works through proxies. What it is for, and what breaks if you block it."
---

Core networking

# mask-api.icloud.com

`mask-api.icloud.com` is an iCloud Private Relay host. Apple lists it on TCP port 443 for iOS, iPadOS, macOS and visionOS, and marks it as supporting proxies.

Run by Apple · Ports: 443 TCP · Checked: 1 November 2026

## Short answer

An iCloud Private Relay host on TCP 443. Unlike the relay hosts, Apple says that it supports proxies.

Block with care

Blocking it can stop iCloud Private Relay from working. Apple doesn't document its exact role.

Matches

`mask-api.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-api.icloud.com` in its iCloud section, for iCloud Private Relay.

Apple marks it as supporting proxies. The two relay hosts, [`mask.icloud.com`](https://kilobat.app/hosts/mask-icloud-com), don't have that mark.

Apple doesn't say what this host does. The `networkserviceproxy` man page says that the daemon downloads its configuration from the internet; Apple doesn't say from which host.

## 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 it can stop iCloud Private Relay from working. Apple doesn't document its exact role.

What breaks if you block it

- iCloud Private Relay may fail to set up or connect.

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

Kilobat doesn't guess at an undocumented host's role. This page describes only Apple's list.

To turn off Private Relay on one network, 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)
- networkserviceproxy(8), man page installed with macOS 27.2

Checked on 1 November 2026.

## Related

- [mask.icloud.com](https://kilobat.app/hosts/mask-icloud-com): The iCloud Private Relay hosts. With Private Relay on, Safari browsing and DNS lookups go through them.
- [iCloud Private Relay breaks some websites](https://kilobat.app/guides/icloud-private-relay-sites)