And while the amount of free storage (2GB) isn't much, you can top this up by referring Dropbox to friends (500MB for each friend, up to 16GB in total) or completing the Getting Started tutorial (250MB). Uploading photos automatically nets another 3GB.
The Carousel application is a neat dashboard for viewing, sorting and sharing images, while content is encrypted in transit and at rest.
Dropbox isn't perfect, especially given the limited free data, and the inability to control how files are presented, but there are few cloud services this versatile.
How to back up your Apple photo library with Box
Box offers more free storage than Dropbox with 10GB on joining, while the 100GB which arguably betters Dropbox's offering. The web UI is simple and easy to organise, and it offers desktop sync software and strong security. Files are AES-256 encrypted in transit and at rest.
However, Box is badly let down by having no option to sync by default - instead, you must log in and specify which folders you want to upload.
How to back up your Apple photo library with OneDrive
Microsoft's OneDrive might be a mainstay of Windows devices but it is a strong cross-platform service with numerous benefits.
For example, Office365 subscribers get 1TB of OneDrive storage, new users receive 5GB free. The service also promises full image back-up, and supports Two-Factor-Authentication (2FA), which is an extra security layer.
You must have a OneDrive account, while security-conscious will be aware of the on-going court cases with the US government on data sovereignty.
How to back up your Apple photo library with Google Drive/Google+
There are numerous advantages of using Google Drive for backing up photos; the prices are reasonable, there is unlimited storage for 'standard' image sizes, and agenerous 30GB of free data, while you can tweak the quality of uploads using 'Auto Awesome' mobile apps. It also supports 2FA.
The disadvantages are that the 30GB is spread across Gmail, Drive and Google+ Photos, full-size images cost money, and you'll need a Google+ account (which you'll already have if you use Gmail).
Crucially, there's no way to automatically upload photos from phone to Drive. You should instead use Auto Backup feature in G+ apps, which will send photos to your rarely-used G+ profile.
How to back up your Apple photo library with iTunes
Backing up your photo gallery to iTunes is a viable alternative to iCloud, especially if you have a large number of files.
The process involves plugging your iOS device into your Mac/PC, selecting iTunes. However, these USB back-ups only happen when you sync your device, which some people rarely do.
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