It works on Windows and Mac computers but also mobile devices like Black Berry, i OS, Android, Nokia, and Kindle.
You can also join chat rooms, send stickers, make audio only calls, and set up group chats.
However, if you do have a Mac, i Phone, or i Pod touch, you can easily make video or audio calls from the device, almost in the exact same way you would make a regular phone call.
You'll be told of any plugin you may be required to download to make it work.
Like Skype, you can make phone calls to non-oo Voo users (like landlines) if you want to pay a fee.
Otherwise, oo Voo to oo Voo video and audio calls are completely free. For example, oo Voo lets you call a Mac computer from a Windows computer, or an Android phone from an i OS phone.
Skype is the most popular app for voice and video calling.
In the mobile market, Skype has since long been dethroned by Whats App and Viber, but it still remains the most prominent tool for free communication on computers.
It's as easy to use as selecting a contact from the "Viber Only" section of your contact list, and then using the video button to start the call.