Just throwing this out there since you mentioned 'YouTube' and 'running in the background'...
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<br> Launch the YouTube app, tap your avatar at the top right, Settings &gt; Background &amp; downloads &gt; Playback. If it's set to 'Always On', switch it to 'Off'.
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<br> The YouTube app supports background playback (I guess for listening to music videos?), and the default is to automatically play another video after the one you're watching ends. So if you just back out of the app without first stopping the video, it may continue to play in the background (as evidenced by a persistent media notification) and it may continue to do so until you've seen every video available on YouTube.
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<br> That could easily account for the battery drain.
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<br> Please don't do that.
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<br> As
<a href='
https://androidforums.com/members/256472/' class='username' data-user='256472, @Mikestony'>@Mikestony</a> mentioned above, Android
<i>should</i> be able to manage background processes, memory, and battery usage on its own. If you step in and start trying to 'optimize' things you may actually wind up making Android work harder to keep everything running.
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<br> There will likely always be apps that don't behave
<i>quite</i> right, but by and large it's typically best to just leave Android alone to manage things as it sees fit.