Google today officially introduced Google Drive - a cloud service that offers up to 16TB of storage for photos and other online content.

Google Drive goes head to head with rival cloud services such as Dropbox and Microsoft's SkyDrive. It offers 5GB of storage for free. People pay on a rising scale for more space.

Google Docs is built right into Google Drive, so users can work with others in real time on documents, spreadsheets and presentations. Users can add and reply to comments on anything (PDF, image, video file, etc.) and receive notifications when other people comment on shared items.

Google Drive can be installed on a Mac or a PC and the Drive app can be downloaded an Android phone or tablet, with the app also coming to iOS devices soon.

A screen reader also allows blind users to access the service.

Drive also features a search feature that can search using keywords, along with a filters (file type, owner and more). Drive can even recognize text in scanned documents using Optical Character Recognition (OCR) technology.

Users can choose to upgrade the 5GB free storage offer to 25GB for $2.49/month, 100GB for $4.99/month or even 1TB for $49.99/month. When you upgrade to a paid account, users' Gmail account storage will also expand to 25GB.

By contrast, Microsoft offers yearly contracts. It charges $50 for maximum storage of 100GB.

Dropbox offers individual users up to 100GB at a rate of $19.99 per month or $199 per year. It also sells larger amounts to groups with the cost and size determined by how many people share the space.

Drive is also working with other Google serices such as Google + and Gmail. Users can attach photos from Drive to posts in Google+, and soon they will be able to attach stuff from Drive directly to emails in Gmail. Drive is also an open platform, so Google is working with many third-party developers so users can do things like send faxes, edit videos and create website mockups directly from Drive.

For more information visit drive.google.com/start