What is trustd and why is this process running on my Mac?

When looking into the Activity indicator You noticed the trustd process from macOS and now you want to know what it's all about? No problem! Because here you can get all the important information about this background process on the Apple Mac. By the way, you don't have to worry about it being... malicious software acts. The trustd process of the Apple Mac is intentional and also quite important in order to make the use of the macOS system in connection with the Internet secure.

The trustd process on the Mac: Management of certificates and digital signatures on the Mac

If you use the Internet, e.g. For example, if you want to access a website via a web browser, then this most likely happens via the Hypertext Transfer Protocol (HTTP) or its encrypted version HTTPS. The latter has been standard for years and is intended to ensure that the connection to websites is established securely. In order to prove the encryption and security of the website connection, not only is https:// used instead of http:// in the URL, you will also find a lock symbol in the address bar of your browser (e.g. in Safari on the Mac). you can click on.

If you click on the lock next to the URL of the website you are visiting, you will be informed that Safari is establishing an encrypted connection to it. To find out more about the associated certificate, click on “Show certificate”. In the overview you get, you can get all sorts of information about the https certificate of a website, especially if you open the “Details” directory below. I won't even pretend that I can explain all the data given there to you. But I can tell you that the ability to query encryption certificates helps increase security on the web.

The trustd process exists so that the Apple Mac can deal with the certificates. Its name is made up of “trust”, the English word for “trust”, and a “d” for the identification as a daemon. A daemon is a process automatically loaded by the macOS operating system that independently performs specific tasks. There is more on the topic here: What is a daemon? The trustd daemon is since macOS 10.12Sierra Part of the Mac system and, in addition to web certificates in the browser, also manages secure connections for the Mail app and the Messages app as well as digital signatures of software updates, third-party apps and similar verifications.

Which certificates macOS trusts

There are two ways to view the certificates trusted by macOS or Apple. The first and quickest option is to access the support document 103272 titled “Available Trusted Root Certificates for Apple Operating Systems.” In addition to further information on the topic, there are various links to the individual certificate lists for various macOS, iOS, tvOS and watchOS versions. Currently, in March 2024, you will find the valid list for macOS 14, iOS 17, tvOS 17 and watchOS 10 with this link.

The second option is to view the certificates on the Mac you are using. To do this, you call it in the Finder Macintosh HD open it, open it Programfolder and within it Utilities-Folder. Now open the system app Keychain management. For the various points in the sidebar (left), there are individual entries in the tabs “My Certificates”, “Keys” and “Certificates” (right). By double-clicking on the individual entries you can access the details about them - very similar to the https certificates in the web browser. But here too there is individual information that I would have to research myself in order to understand it.

Problem: The trustd process causes a high CPU load of up to 100%

The Apple Mac's trustd process should actually run unnoticed in the background and not be noticeable. However, in rare cases it can happen that a digital hiccup occurs and this becomes noticeable in a high CPU load. If he exhausts the processor so that there is a high number next to his name in the CPU column in the activity display, then you can end him directly within the overview (double-click and then use the “Exit” button). If several trustd instances are listed, you can terminate them one after the other. Don't worry, the process will restart automatically.

To force all trustd instances to restart in one fell swoop, you can also use this Port terminate with a command. This is:

sudo killall trustd

If you don't want to mess around with the macOS processes, then you still have the most obvious solution: restart the Mac.

Conclusion: The trustd process is an important part of macOS

Regardless of whether it is website certificates, digital signatures of software installations and updates or the connection to mail and messaging servers - under macOS on the Apple Mac, the trustd process regulates the checking and verification of these matters. It is therefore an important part of the system and the use of the Internet. The same applies to the use of this process or its counterparts in iOS on the iPhone, iPadOS on the iPad, tvOS on the Apple TV and watchOS on the Apple Watch. 

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