Designing macOS Menu Bar Extras

A great article by Marc Edwards, essentially the “missing manual” for macOS menu bar extras:

Apple’s HIG is great, but it doesn‘t contain much information related to designing menu bar extras. This article aims to provide additional details and context needed to create icons for macOS menu bar extras.

There are a lot of subtleties to get right, and this will help you if you are unfamiliar with the conventions!