There are many online backup and file sharing sites but this one known as Dropbox is the most popular amongst the users who are using it so far.
Dropbox is more than just online backup as it is the combination of file sync and file sharing service along with the backup service. Dropbox is software that syncs your files online and across your computers. Put your files into your Dropbox on one computer, and they’ll be instantly available on any of your other computers that you’ve installed Dropbox on (Windows, Mac, and Linux too).
The simplicity with this site makes this the most popular amongst the users. Backed up files can also be accessed through the website which is good for those who want to access the files from the computer not having Dropbox installed.
Though the service doesn’t provide the unlimited storage but it should be the best to use when backing up important files and folders.