There have been screen-sharing services before, allowing you to view the desktop of a friend or colleague's computer anywhere else on the internet — but few that offer true multi-platform support. New to the burgeoning market is UK company Yuuguu, with its free app that enables Windows, Mac and Linux computers to interact together.

With the Yuuguu Java-based client software installed on two computers, it's possible for one party to initiate an instant messaging session, and then you can share the screen of either computer, so that both users will see the same desktop and any running programs. This facility comes into its own for virtual presentations, or team collaborations on document writing and editing.

Due to the bandwidth limitations, though, don't expect to be able to watch motion video from afar. Traditionally, remote viewing of a screen has been possible with the VNC (virtual network computing) protocol — but this requires some careful setting up and is especially challenging when it comes to tunnelling through corporate firewalls, or even home routers.

What makes Yuuguu's system particularly attractive is that it works over a common web browser port (port 443, used for secure https transactions) so is unlikely to suffer from blocked port issues. And installation of the software does not require admin privileges on Mac or Windows platforms so can be readily installed by anyone.

We set up a Mac and a Windows PC to test the system. After downloading and installing the app, you need to register an account with Yuuguu, typically using your e-mail address as a login name. Yuuguu keeps a central database of registered accounts, through which you can contact other users.

In order to reduce latency in screen refreshes, the default colour depth of the viewed screen is set to 'fast' 8-bit mode, which renders colours rather poorly. If you want to keep this speed, we'd recommend switching to a plain colour desktop pattern. And there is an inevitable lag between control actions on the host machine and results on the client — in our test, about two seconds. But overall, the system worked impressively well, with a relatively intuitive interface assisting the operation.

Additionally, even without installing the software, anyone can still view a Yuuguu user's screen using the Web Share feature via a web browser window, although this only works for passive viewing. A unique number is generated when you initiate a session, which can be entered into a text field at www.yuuguu.com/share to authenticate to the correct computer.

The latter feature relies on Adobe Flash to show a real-time video of the remote user's screen, and has a longer latency, up to eight seconds when we tried.