How can I speed up a very slow Font Book Font Book is dead slow when looking for fonts. I noticed I have some 350+ fonts installed. Most of these I never use at all. My Mac is a 8 GB 1,7 GHz Midt-2014 MacBook Air.

Would it help to throw out a lot of these fonts? (Will macOS even let me do this, since most/all of them actually seem to be installed by macOS and subsequent updates?)

Is there anything else I can do to speed up Font Book? (Is this a performance issue that should be reported to Apple?)

~/Library/Fonts: 0 fonts
/Library/Fonts: 227 fonts (three groups of files dated 2012, 2014 and 2016)
/Library/Fonts/Microsoft: 160 fonts (all dated 2011)
/System/Library/Assets/com_apple_MobileAsset_Font3: 6 fonts (just installed)
First of all don't go into that directory and start deleting fonts. Assuming SIP will even let you, those are the fonts that ship with the Mac. Unless... have you installed some fonts there yourself?

Fonts should be stored in /Users/[USERNAME]/Library/Fonts.

And you can safely remove any and all fonts from that directory, just leave the directory itself.

If you have been installing fonts in the /System folder you probably want to go in there and move the ones you installed there to your /Users fonts folder. In case you were wondering here is a list of fonts that macOS ships with.

Should you somehow mess things up, Font Book.app has a function in the File menu called "Restore Standard Fonts..." which can be used if you think you may have messed up and deleted fonts you should not have deleted.