When it comes to cloud storage, users are spoiled for choice. Collaboration features, cheap (or even unlimited) storage, pure online backup, privacy -- you can easily find a service that meets your needs. With so many options (including dozens of cloud storage companies touting everything from free storage to syncing), choosing a single service can be overwhelming.
Aside from simply backing up files in the cloud or to other devices, file syncing is a key feature of many cloud storage providers. If you use multiple computers, automated file syncing eliminates the need to transfer files using email or a thumb drive. When you make a change to 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.
Dropbox (2 GB free; $10 per month for 100 GB) is arguably the most well-known file syncing and online backup service, and is our pick for Best Cloud Storage. It's incredibly easy to use, with an intuitive interface and file syncing that lets you store and access files on multiple computers, mobile devices and in the cloud. Downloading Dropbox takes only a few minutes, and backing up your files is as simple as dragging and dropping them into the client. It's one of the few companies to work on Windows, Mac, Linux, iOS, Android and even BlackBerry. Reviewers appreciate the cross-platform support, and you can sync files among computers with different operating systems. The service saves older file versions for 30 days for all subscribers; premium subscribers can purchase the "Packrat" option (Est. $40 per year) for unlimited file versioning that will never be deleted.
As popular as Dropbox is, reviewers say that Google Drive (15 GB free; $2 per month for 100 GB; $10 per month for 1 TB) strongly challenges the storage giant in the cloud storage wars. Google offers far more free storage space than Dropbox (though you can get up to 18 GB free with Dropbox via referrals), and its premium subscriptions cost far less. Google Drive and Microsoft OneDrive (7 GB free; $25 per year for 50 GB) include 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. Dropbox has started offering similar collaborative functions, but there aren't many reviews of these features. There are concerns about Google Drive's privacy policies, and while Microsoft OneDrive works on Macs, its main selling point is that it's integrated into the Windows 8.1 operating system. OneDrive is so easy to use with PCs and Windows Phone -- and is so beautifully designed -- that it wins the Best Reviewed Cloud Storage for Windows.
Dropbox and Microsoft also offer business cloud storage services that focus on services for multiple users: Dropbox for Business and OneDrive for Business. Dropbox for Business costs $75 per month for five users and unlimited storage, while Microsoft OneDrive for Business is $2.50 per user per month with 25 GB per user (a 1 TB option will soon be available). But a lesser-known name comes out on top in reviews: Box for Business (Est. $15 per user per month for 1 TB) . File-syncing, collaboration, storage space and security are especially important to enterprise and small businesses and Box is strong on all levels, along with offering user controls like restricting who can edit a document.
Dropbox offers a wide variety of plans (including Dropbox Business) and a generous free account (you can earn up to 18 GB free through referrals), and it has a file-synchronization service that will please most users.
Data security is big business and, not surprisingly, has impacted cloud storage services as consumers grow more cautious about their personal information floating out in cyberspace. In light of the National Security Agency (NSA) data mining scandal -- which raised serious questions about how private our communications are -- cloud storage companies are pushing their services as safe and secure.
SpiderOak's (2 GB free; $10 per month for 100 GB) business model focuses on privacy and security; it prides itself on airtight encryption and a "Zero Knowledge" policy for customers. Instead of being stored in a cloud or in the host company's servers, your heavily encrypted files are kept on your computer. As a result, SpiderOak doesn't even have access to your file names, let alone other important information like your password. You can set up a password reminder hint, but if you forget it, you won't be able to access your account.
The program works with Windows, Mac OS X and Linux systems; free Android and iOS apps are also available. In addition to the basic plan, SpiderOak offers business options ranging from $5 to $10 per user per month.
Mega, a newer cloud storage service founded by Megaupload's Kim Dotcom, puts privacy at the forefront as well and uses a similar encryption strategy by encrypting files locally on devices, so it can't ever see the details of what you're uploading or transferring to another machine. Mega offers a generous 50 GB of free storage but doesn't come with many bells and whistles.
Experts say you should also read the terms of service and privacy policies of online storage providers before signing up with a company to ensure you agree with their terms. For example, Microsoft and Apple's privacy policies give the companies the right to scan files. While Google Drive (15 GB free; $2 per month for 100 GB; $10 per month for 1 TB) has strong encryption, it receives the biggest critiques for Google's privacy policies, which are vague about how Google can or can't use your files. Google's ad-based revenue (which pushes ads based on your personal content) is a long-standing concern of privacy mavens. In reaction to the NSA spy scandal and ad-based Internet companies, the Finnish security company F-Secure created a cloud storage company, Younited (free), on a virtual private network.
Encryption is of course critical to your file security, and experts advise using a company with multiple encryption layers as well as password protection. Many cloud storage services encrypt files during transfer but not on your device or on their servers -- although this is becoming less and less common. Some cloud storage services let you devise your own encryption key; if you're tech-savvy enough, this might be a good option.