How much space do apps really use?

Have you ever sat looking at your phone wondering where all the memory has gone? There never seems to be enough and after taking a few photos and downloading a handful of apps, there seems to be hardly anything left. Whatever size phone you get it doesn't seem to have enough memory. Where does it all go to?

Let's look at a an example app. Vine, the new six-second video sharing social networking app from Twitter.

Go to the Apple App Store on the iPhone and find Vine. It clearly states that this is 11.5MB. That is obviously a lightweight app that uses very little memory, so you go ahead and download it.

Run it a few times and watch the clever and amusing videos that people have posted, follow some people and watch some more videos.

Now go to Settings, General, Usage. You can see my phone on the left and Vine, down near the bottom is using 270MB of memory. That's a bit different to the 11.5MB that the App Store says it uses. How come?

Well, 11.5MB is the size of the download. I'm guessing that this is a compressed file that is expanded when it is installed because tapping Vine on the left says it is 14.2MB. So the compressed file expands to 14.2MB.

The app plays six-second video clips and I suspect that it is caching the videos and storing every one I've watched recently. This is not a 14.2MB app as the store states, it requires over a quarter of a gigabyte. That's why all your memory is disappearing fast even though you have only installed a few lightweight apps.

This problem isn't limited to Vine and many other apps cache information and so use up large amounts of memory. Take a look at Podcasts in the screen shot. This is a 9.9MB app, yet it takes up 530MB because of the podcasts it has stored.

This is not an iOS problem either and it happens just as much on Android. On a Google Nexus 7 for example, (other phones and tablets are similar) go to Settings, Apps, and select Google Earth. The app is 9.41MB, but there is a 371MB cache.

Now you know why there is so little memory left on your phone or tablet.