My cursor on my Macbook Pro has a box around it that enlarges everything

Solution 1:

Could this be the Zoom accessibility feature?

It can be toggled with Alt-Command-8.

Also see System Preferences => Accessibility => Zoom for more details and options.

Solution 2:

I just had this problem. I tried everything in Accessibility but I just couldn't figure it out. I was going to give up, but discovered I was leaving out one step. This is what I did and it worked!!

Go to System Preferences => Accessibility => Zoom. Scroll down to Zoom style: You will see two frames. The first one has two options 1) Full screen or 2) Picture in picture. Next to that should be another frame showing OPTIONS. Click on Options. It will show a checklist. The first one is Show Preview rectangle when zoomed out. Deselect it. I did all the steps above and Poof, the rectangle disappeared. Good luck.