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I installed a GIF app from Play Store, and they want permission to do this. I don't even understand what drawing over other apps means.

Is it the floating hearts in a GIF in a private message in Messenger? I'm confused.

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    Drawing over other apps means being able to display something, while not in foreground, like a screen filter that darkens the screen. If an app requests this permission without you seeing a need for it, uninstall this app immediately.
    – GiantTree
    Commented Aug 8, 2016 at 14:21
  • O k So I'm wrong? It's not something like floating hearts or animated movements in a meme or GIF? And if so, why is the GIF app asking permission to draw over another app? What app would they want to draw over and what is the purpose in drawing over?
    – Stacey
    Commented Aug 8, 2016 at 15:01
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    Drawing over other apps allows you to alter the representation of other apps. If the app in question does not seem to need this (I don't know the app you try to describe), don't allow that permission. Displaying GIFs or memes does not require that permission.
    – GiantTree
    Commented Aug 8, 2016 at 15:07
  • @GiantTree Like what Facebook Messenger does when the little profile photo of the person you're talking to keeps hovering over other apps even when you leave the app?
    – Fiksdal
    Commented Aug 9, 2016 at 9:25
  • @Stacey You should report this app as well.
    – Rob Rose
    Commented Nov 16, 2016 at 2:44

2 Answers 2

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The technical name of this permission is SYSTEM_ALERT_WINDOW:

Allows an application to open windows using the type TYPE_SYSTEM_ALERT, shown on top of all other applications. This permission allows an app to show a "popup" window above all other apps, even if the app is not in the foreground. A malicious developer/advertiser could use it to show very obnoxious advertising. Almost no apps should require this permission unless they are part of the Android operating system. An example of a system alert would be the alert you are shown when your phone or tablet is out of battery and is about to shut down.

As GiantTree already pointed out, this is also used by "screen overlay apps" such as screen filters. A malicious app could e.g. use it to trick you to do things you'd otherwise wouldn't do, for example overlaying buttons with different text (or replacing the question text with something different) so you press "yes" on a screen you wanted to press "no" (so-called "Tap-Jacking") – which is why (at least with Android 6) people often get the warning "screen overlay detected". See e.g.:

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GiantTree is right. If the "floating hearts or animated movements" are supposed to appear on top of other apps, then this permission is needed. If that's not what it does or if that's not what you want (i.e., if it's only supposed to be for editing GIFs inside the app), then you should remove/not install the app — such overlays can be used to intercept input and perform unwanted operations on your phone or steal your data.

A classic example of a valid use for this permission is, again as GiantTree mentions, screen filtering. Such apps can darken the screen or red-shift it for use at night. Another example is Facebook Messenger, which can put chat icons on the screen to make notifications more visible and provide quick access to current conversations.

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