Do I need a quit button for Android devices?

I made an app a few years ago and one of the comments was that the user couldn’t quit the app. Is it necessary to add a quit button? Are there some android devices that can’t back out of an app if it doesn’t have an exit button?

Every android device can exit from anything with the Home button. The point of the android multitasking is that you don’t have to exit an application and load it again if you need, just push the home button an it will run in background process. If an adnroid device doesn1t have home button like tablets mid game running, you can just drag the top of the screen to make it appear. So basically you don’t need to add Exit button to your game. (But customers first…)

Strictly you don’t need a ‘quit’ button: as hablint1 mentioned, all android devices have a ‘Home’ button. However some may not have a physical home button, which means that you have to use the software buttons (i.e. the on-screen buttons that appear from the tray when you swipe up from the bottom of the screen). If your game is full screen then according to which settings you chose in Unity, these software buttons are hidden while you play, and an inexperienced android user may not know to swipe up to show them. I think in this case it’s prudent to have a quit button, but otherwise it’s not necessary.

Another concern is that with iOS, devices are designed so that you press the home button to quit , so you definitely don’t need to show the quit button on iOS.

No, its not necessary to add quit button. On android all apps move to background if user quit from it and then it could be instantly resumed or killed by system if it need more memory. So if user want to quit he should to press “home” button.