Quick answer: Press and hold BACK and FAST-FORWARD on your remote for 5 seconds. Long answer:
I just noticed there’s a big increase in people visiting the site looking for answers for why their Fire TV device is zoomed in all of a sudden. Hopefully, they’ll be able to find this post and get a quick fix.
In the latest 18.104.22.168 Fire TV software update, Amazon introduced a new Screen Magnifier to help visually impaired users read small text on their TV. The feature is turned on and off by pressing and hold the BACK and FAST-FORWARD buttons on the remote for 5 seconds. Note that the BACK button is the one to the left of the HOME button.
It seems like a lot of people are accidentally pressing this button combination and are confused why everything on the display is enlarged with an orange border around the screen. If you are having trouble getting the feature to turn off using your remote, you can also turn it off by going to Settings > Accessibility > Screen Magnifier and turning it off there.
You can also press the PLAY and MENU buttons on the remote to zoom back out without turning the feature off entirely.