I have a 16 GB iPhone 4S running iOS 7.1.2 (I don't want to upgrade to iOS 9 under any circumstances). I have the following things on the iPhone: 6 GB of music 750 MB of photos 2.4 GB of apps 100 MB of documents and data Nothing else that I use other than iOS itself Try to guess how much free space I have left. You guessed wrong, I only have 400 MB of free space, and here's why: What the hell is "Other?" I can't believe that iOS takes up almost 4 GB. So what's in there? I remember this used to be much less, more like a few hundred MB. It can't be documents stored by apps because that has its own section. What do I have to delete to get rid of it? This problem is all over the internet but people are just guessing. Some say it's Safari cache, but seriously, could that be all cache? Some say it's Mail attachments, but I checked and I don't have attachments downloaded to the phone. Some say it's Messages conversations, but that's just text. I deleted my messages and it didn't change anything (other than the fact that I no longer have my messages). Others say you should backup and restore, but I'm afraid that will upgrade me to iOS 9. Will it? I don't ever want to risk that option because there's no way of going back.