
There are thousands of fonts available online, both free and paid, and sometimes they don’t work properly on Mac. Sometimes the issue is simply that you’ve installed the same app more than once, and Apple prompts you to remove one of these before validation. When there are problems, you’ll see a message stating what’s going on. After the fonts get installed, the validation process occurs automatically. To use fonts in your apps, you need to install and validate them using the Font Book.

The ability to add new collections is for organization use only. However, this does not affect how the font works across macOS and in apps. You can add new collections to the Font Book, then change where fonts reside. Drilling down further, you see the fonts arranged by collections, including Fun, Modern, PDF, and Traditional.

Unless you’ve already manually added fonts, you’ll find all of your apps in the former category. The list includes system fonts that have already been downloaded and others that you may want to add. The Font Book on Mac is located under the Applications menu on your computer.
