If you try and use Google's new Hangouts app for Android on AT&T's cellular network, don't expect to video chat—because you can't.

Slashgear reports that the video chat capability in the new Hangouts app doesn't work on AT&T's cellular networks, throwing up a message that reads "you must be on a Wi-Fi network to join a video call." It seems AT&T is alone in imposing the restriction, and it's also not an issue in the iOS Hangouts app, but it does affect all Android handsets—including a fully unlocked Nexus 4.

If this all sounds familiar, then it's because AT&T famously blocked Apple's FaceTime over cellular last year. For what it's worth, it did eventually crumble and allow the service over its 3G networks. When The Verge approached AT&T to find out what was going on with Hangouts, it gave a fairly indirect answer:

All AT&T Mobility customers can use any video chat app over cellular that is not pre-loaded on their device, but which they download from the Internet. For video chat apps that come pre-loaded on devices, we offer all OS and device makers the ability for those apps to work over cellular for our customers who are on Mobile Share, Tiered and soon Unlimited plan customers who have LTE devices. It's up to each OS and device makers to enable their systems to allow pre-loaded video chat apps to work over cellular for our customers on those plans.

In other words, if Google has asked nicely, AT&T claims, it would be working—though it's not really clear what criteria the carrier uses to approve apps. Of course, the whole thing suggests AT&T is actively detecting what type of traffic is being sent and received, even from unlocked devices, and is able to reject it. And that's perhaps even more worrisome than being unable to video chat over cellular. [SlashGear via Verge]