Download Caffeine – Keep Screen On from the Google Play Store on your Android device.

The app works via a “Quick Settings” toggle, so first, swipe down from the top of the screen twice to expand the full “Quick Settings” panel.

You should see a Pencil icon somewhere on the panel; tap it to edit the “Quick Settings” toggles.

On some Android devices, like Samsung phones and tablets, you have to tap the Three-dot icon, and then choose “Quick Panel Layout” to edit the Quick Settings panel.

Look for a toggle with a Coffee Mug icon.

Next, move the “Caffeine” toggle to the main “Quick Settings” panel. Tap and hold it to drag it into position. On Samsung phones, you’ll drag the toggle from the top of the screen to the bottom. On Google Pixel and other phones, you’ll drag it from the bottom to the top.

When the toggle is where you want it, tap the Back arrow or Checkmark icon to save.

Now, you can actually use the app. Whenever you want to change the screen timeout length, swipe down from the top of the screen to open the notification panel and “Quick Settings.”

Tap the Coffee Mug icon in “Quick Settings.” By default, the screen timeout will be changed to “Infinite,” and the screen will not turn off.

Tap the Coffee Mug icon again to return to your normal screen timeout length.

Caffeine has a number of other customization options; just open the app to adjust these to your liking.