# What is trustd on Mac?

> trustd checks the security certificates of the websites and servers your apps connect to. Why trustd uses CPU on a Mac, and why several copies are normal.

**Quick answer:** trustd checks the security certificates of the websites and servers your apps connect to, so connections are what they claim to be. It's part of macOS and safe; it's busy when your Mac makes many new connections at once.

From Bondi's Mac guide, reviewed by Noaman Khalil on October 10, 2026. Web page: https://trybondi.app/guide/trustd/

trustd is the part of macOS that checks **security certificates**: when an app connects to a website or server, trustd makes sure the certificate is valid, so the connection is what it claims to be. It's safe.

## Key points

- trustd checks certificates for every secure connection your apps make.
- It gets busy with many new connections at once.
- Leave it running: secure connections depend on it.

## What trustd does

Every padlock in a browser and every secure connection an app makes relies on a certificate check. trustd does those checks for the whole Mac and remembers results for a while, so the next connection is quicker. Several copies run at once: one for the system, and others for each user account, including macOS's own background accounts. That's normal.

## Why is trustd using so much CPU?

Many new connections at once: opening a browser with many tabs, a sync starting up, or an app that connects to many servers.

In one reading of a MacBook Pro (M1 Max, 64 GB) on October 10, 2026, trustd was using **0.0% of the CPU** and **9.4 MB of memory** (the 1 of its 6 copies that could be measured).

## Can I quit trustd?

Leave it running: macOS needs it.

## How to check it

1. Open **Activity Monitor**: press Command-Space, type "Activity Monitor" and press Return.
2. Type **trustd** in the search field at the top right.
3. Look at **% CPU** and **Memory**. Several copies are normal.

## Questions

### Is trustd a virus?

No. trustd is part of macOS: it checks the security certificates of the sites and servers your apps connect to.

### Why is trustd using CPU on my Mac?

Your Mac is making many new secure connections at once, for example a browser opening many tabs. It settles quickly.

### Why are there several trustd processes?

macOS runs one for the system and others for each user account, including its own background accounts. That's normal.

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