The “Restrict background data to WiFi” feature (formerly named “Restrict to WiFi”) allows you to restrict data transfers done by selected applications while they are in the background. It has been introduced in 3GW Pro 1.11.0 and requires Android 2.2+ (Froyo).
To apply it, go to the “usage by application” screen, press on the target application and select “Restrict background data to WiFi” in the menu. To revert to the non restricted state, press on the target application and select “Allow on mobile” in the menu.
The function monitors apps and attempts to terminate their background processes when they start transferring data on mobile networks. Note that:
– Apps will have transferred some data (usually a small amount) before they can be detected and terminated.
– The termination doesn’t require your phone to be rooted, but applies only to background transfers. if you open the app (so it is in the foreground) and it transfers data, it will not be terminated, because it happens while you are here to control what happens, unlike in the case of a background transfer. Android forbids a non privileged application to kill another one, it’s only possible to terminate background processes.
– Some rare applications like Facebook don’t seem to be stoppable. When terminated they obstinately restart again and again. To try to restrict them may actually be counterproductive (more data transfered!) and it is suggested to not attempt to restrict them.
To summarize, the “Restrict background data to WiFi” feature is not a firewall which can totally block an application. It attempts to reduce the background usage of an application, and will usually succeed, except for some applications like Facebook (unfortunately we have no comprehensive list of apps concerned).