There are so many gigabytes of free online storage space available these days from Google, Microsoft, Dropbox, and several other cloud service providers. Picking just one service--especially if you're going to upgrade to a paid plan--might be confusing, since these services all offer similar features and are designed to do the same things: Make accessing your files from anywhere a cinch, provide online backup for those important documents and files, and also help you share files with others very easily. Here's are the highlights of each of the most popular online storage and file syncing services so you can pick the right option for your needs. ~ updated September 24, 2014

Note: Several of these services are also featured in our Top 7 File Syncing Apps article, which also includes desktop software you can use to sync your files offline. The apps below all store your files online and not all of them include syncing capabilities.

•Amazon Cloud Drive

Cloud Drive is Amazon's online storage service you can use to upload music, photos, videos and documents through Amazon's website interface. A key feature that separates Cloud Drive from other services is you can store an unlimited amount of MP3s on Cloud Drive without them counting towards your storage usage. Paid storage plans include unlimited space for music you upload (whether bought from Amazon or not). You can listen to your music anywhere with Amazon's Cloud Player online app. There are also Android and iOS apps for your photos.

• Best for: Music lovers who who want to backup their music MP3s and access them online; cheap online storage
• Free space: 5GB
• Paid storage plans: From $10/year for 20GB up to $500/year for 1,000GB
• Platforms: Web, Android, iOS

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•Box

Box (formerly Box.Net) is used by many businesses and professionals to securely store files online and share them, because of unique project collaboration features, content access controls, and easy file sharing (you can share files with just a link and entire folders of files, with updates of when users access your files). 10GB of free storage is available for personal or business use, but Box has run promotions in the past to increase that free storage space to a whopping 50GB. 

• Best for: Storing a large amount of files online and sharing them with co-workers; cheap online storage
• Free space: 10GB (note: 250MB file upload size)
• Paid storage plans: $10/month for 100GB (and 5GB file upload size) plus enhanced features; business plans also available 
• Platforms: Web, iPhone, iPad, Android

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•Dropbox

Dropbox is the online storage and syncing service that most competitors are compared to. This is thanks to Dropbox being one of the earliest services of its kind, its drop-dead simple syncing, integration with lots of third-party apps, and numerous ways to rack up extra free space (including .edu referral bonuses, uploading photos and videos, and setting up your own Google AdWords campaign to quickly get more referrals). However, if you don't get extra free space using referral tricks, the paid plans are among the most expensive offered and if others share Dropbox with you, that folder's storage space counts against your storage limit.

• Best for: File syncing and online storage you don't have to fuss with or think about too hard. It just works (put a file in your Dropbox folder and it's uploaded and synced; click to get a link to share files); getting the most amount of space for free with some tricks.
• Free space: 2GB
• Paid storage plans: $9.99 for 1TB
• Platforms: Web, Windows, Mac OS X, Linux, Android, iPhone, iPad, Android

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•Google Drive

Google Drive is the latest online storage and syncing service, offering unique features like integration with Google Docs and Google+, as well as optical character recognition (OCR) of your scanned documents. The integration with Google Docs means you can edit and create doc files from within Google Drive. Google Drive also has a huge max file size of 10GB. Pricing is also pretty competitive, especially if you paid for more Gmail or Picasa storage before April 24, 2012 when Google announced Google Drive (on the old grandfathered storage plan, 20GB of extra storage is $5 a year versus the $2.49 per month on the new plan).

• Best for: Google Docs users, uploading large files, an enormous amount of storage capacity
• Free space: 15GB (shared across other Google services, such as Gmail)
• Paid storage plans: From $2.49/month for 25GB to $799.99/month for 16TB
• Platforms: Web, Windows, Mac OS X, Linux, Android, iPhone, iPad, Android

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•iCloud

iCloud is a unique service for Apple device holders: iCloud automatically syncs contacts, photos, calendars, documents, apps, music, and more across your iPhone, iPad, and iPod touch devices running iOS5, as well as Mac OS X and Windows PCs. One of the best features of iCloud is its automatic backup and syncing of these key types of files--especially your apps.

• Best for: Backing up and syncing Apple devices
• Free space: 5GB
• Paid storage plans: From $3.99/month for 200GB to $19.99/month for 1TB
• Platforms: Web, Windows, Mac OS X, iPhone, iPad

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•Microsoft OneDrive

Microsoft's OneDrive offers one of the most generous amounts of free space for new users: 15GB, and even more for existing Live/Hotmail users: 25GB. OneDrive offers unique in-browser creation and editing of Microsoft Office documents via Office Web Apps (no need to have the software on your desktop). Syncing OneDrive is as simple as Dropbox now, with one catchall OneDrive folder for all your files. Paid plans for extra storage space are also really cheap compared to the competition.

• Best for: Microsoft Office users, the most default free space for online backup and syncing
• Free space: 15GB to 30GB (depending on promotion)
• Paid storage plans: From $1.99/month for 100GB to $6.99/month for 1TB (including Office 365 Personal)
• Platforms: Web, Windows, Mac OS X, iPhone, iPad

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•SugarSync

SugarSync is a robust online storage and syncing service with a couple of standout advantages: You can select which folders to backup and sync (rather than having to place all your files in one folder, like Dropbox and SkyDrive), permissions and password setting for shared folders, and numerous mobile apps. Unlike the other services, there's no max file size limit restriction; however, paid storage is a bit pricey. Update: SugarSync is no longer free, unfortunately. 

• Best for: Users who want a bit more control over their syncing and backup or need to upload files with enormous sizes
• Free space: N/A
• Paid storage plans: From $4.99/month for 30GB to $14.99/month for 100GB
• Platforms: Web, Windows, Mac OS X, iPhone, iPad, Android, BlackBerry, Windows Phone, Symbian, Kindle

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•Other Online Storage and Syncing Options

In addition to the very popular services above, there are also many others you may want to consider, including:

• Minus is designed for simple file sharing--you can drag and drop files to the webapp or use the apps for Windows, Mac, Ubuntu, Android, iPhone, and iPad. It comes with a huge 50GB of free storage space and a file upload size limit of 2GB.
• SpiderOak offers the most security-centric service, with a "no password storage" policy and 2-factor authentication to make it impossible for SpiderOak employees to ever access your data. 2GB of storage space is offered for free.
• Wuala syncs your locally encrypted files online and offers a unique way to gain extra space beyond the 1GB free space offered: Exchange the unused storage on your computer for more Wuala space. Available for Windows, Mac, Linux, Android, and iOS