File synchronization is becoming very popular, and new providers are entering the market all the time. If you use multiple computers, file syncing eliminates the need to transfer files using a thumb drive. When you make a change on a file on your work computer, for example, that file will automatically be updated on the service's online interface, your home computer, your laptop and the service's mobile apps. Usually, the backup and syncing feature is restricted to files in a single designated folder. However, unlike backup-style storage services like Carbonite, syncing-style cloud storage services often have no limits on the number of PCs or mobile devices you can use, only on the amount of data you can store with the service.
Most file syncing services offer at least 2 GB of free online storage and several offer 5 GB of free storage or more, making them a good choice for backing up small amounts of data. More storage space can be had by upgrading to premium subscription plans. However, these services are typically more expensive than basic online backup services like Mozy and Carbonite, and none offer unlimited storage plans or encryption options beyond SSL transfers.
Dropbox (Free for 2 GB) has long been one of the most popular options among file-syncing services, earning Editors' Choice awards and accolades from almost all who review it. You can often earn more free storage by recommending friends or helping Dropbox beta test new features. If you need a lot more storage space, Dropbox offers paid subscriptions for 50 GB (*Est. $10 per month) or 100 GB (*Est. $20 per month). The service saves file versions for 30 days for all subscribers; premium subscribers can purchase the "Pack-rat" option (*Est. $40 per year) for unlimited file versioning that will never be deleted.
Reviewers say Dropbox is a snap to use. Downloading the software takes only a few minutes, and backing up your files is as simple as dragging and dropping them into the client. The status of each file is easily recognizable, with backed-up files indicated by a green checkmark. Dropbox is also useful for sharing documents with others, because you can send files directly from the client (which allows them to be edited) or create a read-only public link. In addition to the usual Android, Mac, iOS and Windows support, Dropbox is one of the few cloud storage services to support Linux computers and BlackBerry phones. Reviewers appreciate the cross-platform support, and you can sync files among computers with different operating systems. This is helpful if you have a PC at work and a Mac at home, for example. Dropbox is more expensive than other cloud syncing services, but reviewers say it's worth the price if you need file syncing.
As popular as Dropbox is, reviewers say that two synchronization services recently surpassed it in the cloud storage wars: Google Drive and Microsoft SkyDrive. They offer more free storage space than Dropbox, and their premium subscriptions cost less. What's more, Google Drive and SkyDrive include very functional productivity tools that allow you to edit documents, spreadsheets, slideshow presentations and other files from within your browser -- and because it's all stored online, the two services include features that let you collaborate with others to edit files together in real time.
Of the two services, critics prefer Google Drive (Free for 5 GB). If you need more space, Google Drive offers a plethora of premium options; $2.50 per month nabs you an additional 25 GB of space, $5 per month unlocks 100 GB, and the plans continue to go all the way up to 16 TB (*Est. $800 per month), which is significantly more than most users (and many businesses) need. If the Google account you use with Google Drive has a Gmail account associated with it, the Gmail account's storage space will automatically be boosted to 25 GB when you buy a premium Google Drive subscription. The deep integration with ad-supported Google products raises privacy concerns with some reviewers.
Google Drive is basically a beefed-up version of Google Docs, the company's online editing suite. In addition to PC and Mac clients that offer the same drag-and-drop functionality as Dropbox, an Android app lets users browse their files and upload photos and videos. (An iOS app is forthcoming.) The service saves your file versions for 30 days or 100 revisions; if you delete a file, it's moved to a trash folder, where you can either erase it completely or restore it to its original location.
Reviewers love Google Drive's powerful search feature, which scans the text of documents as well as file names, and experts also appreciate that changes in collaborative documents appear in real-time as people type. Google Drive can open more than 30 different file types on its own -- no plugins or additional programs required -- and the maximum file upload size is 10 GB, far more than the 2 GB (or less) supported by other syncing services. It doesn't, however, support media streaming.
Microsoft SkyDrive (Free for 7 GB) has its share of fans, too. The service, which offers the same basic functionality as Google Drive, gives users more storage space for free, and if you owned a SkyDrive account prior to the service's April 2012 update, you can opt to grandfather your account into a free 25 GB of space. The storage prices for its 20 GB (*Est. $10 per year), 50 GB (*Est. $25 per year) and 100 GB (*Est. $50 per year) subscriptions are even cheaper than Google Drive's, although it doesn't offer the same wealth of upgrade options as its rival. SkyDrive apps are available for iOS and Windows Phone 7, but Android users will have to opt for a third-party SkyDrive solution or use the mobile web interface, which offers less functionality than the apps.
Experts say that SkyDrive's in-browser editing should feel very familiar to Windows users, as it mirrors the look and feel of the latest iterations of Microsoft Office. The Microsoft Web Apps aren't quite as robust as Google's productivity tools, however; fewer file types can be opened in-browser, collaborative edits don't appear until both parties save and refresh their work, and file versioning is limited to the last 25 revisions, albeit with no time restraints. One unique feature lets you remotely access any PC you've installed the SkyDrive app on, assuming it's connected to the Internet and you've remained signed in to the service. Experts say Microsoft Office fans and cloud storage seekers looking for the most storage bang for their buck will be very happy with SkyDrive.
SugarSync (Free for 5 GB) is another popular option for Windows and Mac PCs, offering the highest degree of customization for users. This syncing-style online backup service lets users choose which folders to back up, rather than limited the synchronizing to a single predetermined folder. After the initial save, files are automatically backed up when any changes are made. SugarSync saves up to five previous versions of each file, although only the current file counts toward your storage total. SugarSync offers a variety of pricing plans, including a 30 GB subscription (*Est. $5 per month), 60 GB (*Est. $10 per month), 100 GB (*Est. $15 per month) and more; business plans and discounted yearly subscriptions are also available. Each plan has a 30-day free trial. SugarSync works on Macs or Windows PCs and offers iOS, Android and BlackBerry apps.
File transfers are a bit slow compared to other online backup services, but experts love the clean, easy-to-use interface. SugarSync can also stream music stored on its servers and allows you to share file access with other people. "If you're looking for the ability to sync and also backup multiple folders around your computer, SugarSync is head and shoulders above the rest," Ellis Hamburger writes in a comprehensive cloud storage roundup at TheVerge.com. SugarSync also wins Editors' Choice awards at PCMag.com and Techlicious.com.
People who have invested heavily in the Apple ecosystem should consider the company's iCloud service (Free for 5 GB), which synchronizes data and files between your Apple apps -- and only your Apple apps -- across multiple devices, including Windows PCs. For example, it will sync a document created using Pages or iWorks, but not Microsoft Office; your iOS and Mac Calendar, email, Contacts and Photos also sync between your connected Apple devices. You also get a free Me.com email address when you sign up for the service. File versioning isn't supported, so there's no way to restore older files you delete or save over.
Apple iCloud gives you the option to store your iTunes-purchased music on Apple's servers, then stream them to up to 10 iOS devices; an upgrade called iTunes Match (*Est. $25 per year) lets you sync up to 25,000 songs you own with Apple's servers, whether they're purchased through iTunes or not; they can then be streamed to any device you log in to with your Apple ID. Songs in the iTunes database don't need to be uploaded, and if Apple has a higher-quality version of the tune in its database, it'll stream that rather than your low fidelity file.
Storage upgrades are available in 10 GB (*Est. $20 per year), 20 GB (*Est. $40 per year) and 50 GB (*Est. $100 per year) increments, which are added to your free 5 GB. Experts say that users with multiple Apple devices should definitely sign up for at least the free 5 GB, but caution that iCloud is severely limited in functionality compared to traditional cloud syncing services. For that reason, virtually all experts recommend using iCloud in conjunction with another Apple-compatible synchronization service, such as Dropbox or SkyDrive.