My university used something called Lockdown Browser. It was free to download for students. On Windows (can't remember if there was a Mac, and it definitely wasn't available on Linux), it could only run after a UAC prompt. It used the webcam and microphone on a computer to record the student. It also used facial detection. I'm pretty sure it also recorded the screen, at least inside the browser window.

It also had options that instructors could enable that had us students have to record a video of our immediate surroundings and have to take a picture of a photo ID with our name and picture (preferably our student ID).

If you did the three-finger touchpad swipe (which I've done accidentally before) to change to a different window or minimize the program, it'd refocus itself immediately, a warning would pop up and tell you that, if it happened a second time, the exam would be closed and the instructor would be notified.

If it detected certain applications running (ex. Discord, WhatsApp, Xbox Game Bar, etc.), it would ask to force close them or it wouldn't run.

Barring a situation in which cheating was possible (ex. the three-finger swipe mentioned above), the browser could not be closed until the exam was submitted.

If instructors chose to use Lockdown Browser, students wouldn't be able to open the exam unless they were using that browser.

So it was still possible to cheat (not that I did, but I'd heard of people who did and how they did it), but still difficult.