The first smart TVs powered by Firefox OS have gone on sale today in Europe. They will be available around the world "in the coming months." This isn't just some token gesture, either: Panasonic's top-of-the-line TV, a curved 65-inch 4K monster, is powered by Firefox OS.

All in all, there are six models of Panasonic Viera TV that have their smarts provided by Firefox OS: CR850, CR730, CX800, CX750, CX700 and CX680. This accounts for almost all of Panasonic's new TVs, and they all sport 4K panels as well. The flagship CR850 (curved) and CX800 (flat) will set you back £3500 and £3200 respectively; the other models span the pricing gamut, all the way down to around £700 for a 40-inch CX680.

Early previews suggest that Panasonic's new 4K TVs are pretty good, especially the top-end models with 10-bit colour (which Panasonic calls "4K Studio Master"). The full reviews should start to appear soon, however.

And then there's Firefox OS. For most consumers, Firefox OS for TVs will be much like any other smart TV platform. The video below gives you a basic introduction. Just like Firefox OS for smartphones, every app is written in HTML5. The new Panasonic TVs ship with a decent number of Firefox OS apps, including a Netflix app that supports 4K streaming, and there's an "apps market" if you want to download some more.

One notable feature of Firefox OS for TVs is that anything (an app, a browser bookmark, a TV channel, an external source) can be pinned to the home screen. Obviously, you also get the Firefox web browser—but as with every other smart TV offering, performance will vary depending on the chip that's powering it.

Firefox OS was originally envisioned as a smartphone OS, but in early 2014 Mozilla announced it would also be coming to some other platforms, such as TVs. The segue doesn't seem overly logical to us—the UI and UX are completely different—but it is probably part of a larger drive to get more people using Mozilla products, similar to how Canonical is attempting to bring Ubuntu to TVs. In January 2015 at CES, Panasonic showed off its first Firefox OS TVs, and now here we are. Mozilla hasn't yet announced any other smart TV partners.