I recently added iCloud storage in preparation for a new iPhone. As part of the process I backed up an iPhone 6. To my surprise the backup took up about 35GB of iCloud space, so much that I got an alert to upgrade my 50GB plan to 200GB. I went from about 3.5GB of iCloud use to 50GB-plus.
Since iCloud isn't backing up apps, and I'd deliberately set up Photos not to use iCloud for anything but Photo Stream, I couldn't figure out what could take up so much space. It was only after I looked under Settings/iCloud/Manage Storage/Backups that I realized that despite explicitly choosing not to put anything but Photo Stream onto iCloud, the backup had overridden that and uploaded all 35GB on the camera roll anyway without the option to decline.
Had I not found the Choose Data to Back Up—after the initial backup completed—I might've thought I had to buy additional iCloud space. Really, if the backup to iCloud can disregard settings elsewhere, the software ought to ask what data to back up before loading it onto iCloud. It doesn't. So if you find you've got a surprisingly large iCloud backup, photos may be the culprit.
Since iCloud isn't backing up apps, and I'd deliberately set up Photos not to use iCloud for anything but Photo Stream, I couldn't figure out what could take up so much space. It was only after I looked under Settings/iCloud/Manage Storage/Backups that I realized that despite explicitly choosing not to put anything but Photo Stream onto iCloud, the backup had overridden that and uploaded all 35GB on the camera roll anyway without the option to decline.
Had I not found the Choose Data to Back Up—after the initial backup completed—I might've thought I had to buy additional iCloud space. Really, if the backup to iCloud can disregard settings elsewhere, the software ought to ask what data to back up before loading it onto iCloud. It doesn't. So if you find you've got a surprisingly large iCloud backup, photos may be the culprit.