Insanely popular folder synchronization service Dropbox has doubled the amount of free space you get from referring another user to the service. You now get 500MB instead of 250MB of extra space, topping out at 16GB of free space.

The person signing up will also get 500MB of space to start off their account. Pro users will get 1GB of extra space, with the amount of free space capping out at 32GB.

How much space is that, exactly? For every friend you invite that installs Dropbox, you’ll both get 500 MB. If you’ve got a free account, you can invite up to 32 people for a whopping total of 16 GB of extra space.

Pro accounts now earn 1 GB per referral, for a total of 32 GB of extra space. Have you already invited a bunch of people? Don’t worry! Within a few days, you’ll get full credit for every referral that’s already been completed. Boom!

Dropbox says that it rolled out the referral program after it noticed Dropbox spreading the most through word of mouth from current users. It started out giving 250MB, then doubled it for students. Now it is expanding the ‘double space’ program to all of its users.

Dropbox has instructions available on its site for how to share referral links with your friends and family in order to earn yourself more space. We’ll refrain from putting our code in here, as we have already tricked enough people into signing up through our referral code to get the maximum amount anyway.

In all seriousness, this is a great promotional tool for Dropbox and a great way to get more space without having to spend. We’d recommend that you do disclose when you’re using the referral link though, people like to know that kind of thing.