Where will you use it?

Whichever you like, and you can have all of them — one plan covers every device you use it on. The Mac app reads any window on the computer. The Chrome extension reads the tab you are working in and runs on a school Chromebook. Most students on a school laptop want Chrome.

Once, the first time you open it, the way macOS does for anything downloaded from the web: “are you sure you want to open it?” Click Open and it never asks again.

What you will not get is “the developer cannot be verified”. theoremEd is signed with an Apple Developer ID and notarized by Apple, and the disk image carries that proof inside it. The install page walks through it.

Open a math problem, open theoremEd (in Chrome, the Σ icon at the top right; on a Mac, Control–Option–T or the ƒ in the menu bar) and press Look at screen. The first time, it asks permission to read the tab or window you point it at; after that there is nothing to set up. It tells you what it can see, then asks you the first question. Want something to try it on first? Three practice problems, each with a mistake in it.

theoremEd never sees anything you do not point it at. The privacy policy says exactly what it reads and where it goes.

Chrome updates it for you, in the background. Nothing to do.

The Mac app tells you in its panel when a new version is out. Click Update and it installs it and reopens by itself; your code and settings stay. If yours says Download instead, the Mac page has the two steps.