Nowadays people are storing more and more data on their iOS devices. Considering the new iPhones and iPads come with high resolution cameras and the ability to record extremely high framerate video, the BACKUPS of these devices on your computer (when you sync with iTunes) can take up a lot of space. When combined with the smaller-sized SSDs shipping in the baseline MacBook Air and MacBook Pro Retina models, this is a recipe for quickly running out of available storage space on your computer.
The iPhone was released in 2007. Chances are good that you have (or have had) a number of iPhones or iPads in your life since then. There is a chance that backups for these old devices (that you may not even own anymore) are still taking up space on your computer! The good news is that it is very easy to browse current and previous backups and remove old or unnecessary versions at any time through iTunes.
To do this, open iTunes and select “Preferences” from the “iTunes” menu. In the resulting window, select the “Devices” tab at the top.
You will then be presented with a list of current iOS device backups on your computer, some or all of which may be taking up a significant amount of space. (This screenshot from my computer only shows my latest manual iPhone backup — on your computer, older backups and backups from other devices may be listed below with corresponding backup dates.)
In most cases it is safe to delete old backups or backups of devices you may no longer have. Just select the item and then hit the “Delete Backup” button. It will disappear and whatever space it was taking up will become available on your HD or SSD.
I prefer to keep only the latest backup to maximize my available hard drive space while still knowing I can recover from a disaster like a lost/stolen phone or accidental erasure. Others may prefer to keep multiple current device backups (revisions) or recent backups from multiple active devices. Regardless of what is listed, just be careful not to delete your most recent backup(s)! If you do accidentally, it would be a good idea to run another backup right away.