It seems like strange advice: if your phone is full up with rubbish and you want to free some of the storage up, then download even more rubbish. But it works.

A new trick lets people get extra space on their iPhone just by downloading some new apps, and by tricking the phone into believing that it needs to clear up some space.

To do it, all you need to do is to download a big app that takes up more space on your phone than you have left. As soon as you do so, your iPhone will automatically start clearing up much-needed storage space.

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You can see the progress happen in real time, if you head to the Storage options. The amount of remaining space will gradually go up as you see the size of each app go down.

One good app to download is Hearthstone, which is really big and also has the advantage of being free. But you can download any app and delete it as soon as the phone has started clearing up space.

That can include deleting things that are backed up in photos, as well as trimming down different apps' data so that the space can be added. Some apps can get so big that they take up as much as 1GB of space, which is a big problem on a 16GB phone, noted Lifehacker who first noticed the trick.

The new technique is actually an update version of an old one, where you would trick your phone into thinking that you wanted to download a big film. The phone would then look to make space for it by clearing out all of the cruft, and then you'd be able to use that freed up space for whatever you want.

But that stopped working with iOS 10, which was released in September.

The new trick works similarly, but is probably better. The film one required actually buying a film from iTunes, and came with the risk that you'd end up paying for and then inadvertently downloading a film.