Everest is a simple, lightweight, and smart browser extension that will automatically adjust text size according to your distance from the screen, and can automatically adjust the zoom level based on the distance between the user and the screen. It is the easiest way to zoom pages up and down, and you can have a custom distance, too. It works in Chrome and Firefox, but does not work on Safari or Edge, and requires a webcam to work.

Once installed, you can add a new option in the Options page of the extension. You will then be asked for permission to use your webcam, and your current zoom level. You can stop monitoring the user by setting it to False.