YouTube Caches Videos

I noticed that my Nexus 5 uses a lot of storage for cache and I wanted to see which Android app caches so much data. It turns out that YouTube used 269MB for cache. I didn't use YouTube's offline feature for music videos, so it seemed strange to see that YouTube suddenly caches a lot of data.

It turns out that YouTube's mobile app for Android now caches the videos you watch. If you watch a video again, YouTube no longer has to download the same chunked files: it uses the cache. After watching a video, I switched to the airplane mode and I could play the video offline, even if it's not supported by YouTube Music Key.

Even YouTube's desktop site started to cache videos again. Since switching to adaptive streams (DASH) in the HTML5 player, YouTube downloaded videos every time you watched them, wasting a lot of bandwidth.