Google today launched a new Hangouts app for Chrome on Windows as well as Chrome OS. You can download the app now directly from the Chrome Web Store.

The reason this app only works if you have Chrome on Windows or Chrome OS is down to how it’s built. For those who don’t know, Chrome apps are written in HTML, JavaScript, and CSS but launch outside the browser, work offline by default, and access certain APIs not available to most Web apps.

This does lead to a few annoyances; the app has to be launched from the Chrome App Launcher, and you need to be signed into Chrome to be signed into Hangouts. When we downloaded the app and hit “Sign in” (as you can see below), a new browser tab opened up in Chrome asking us to sign in there.

The Hangouts app features a “streamlined design” to keep your chats accessible regardless of what you’re doing (again, because it’s a Chrome packaged app, it works outside the browser so your chats are always available). The contact list and chats are condensed into one window, with notifications that alert you to new messages. Chats sync across Hangouts on all your devices.

The best feature is probably calling on the desktop, which now has all of Hangouts’ video and voice functionality. This means you can make phone calls to any number in the world (via Hangouts dialer) right from your computer. The app even includes complete Google Voice support, so you can make and receive calls and get your voicemails and SMS messages directly in Hangouts.

The release brings Google’s chat service to the desktop in a new way. As the company puts it: “When you’re chatting with your friends and family, you want your conversations easily accessible, not buried in browser windows.”

While Google has had a Hangouts Chrome extension for a while, this is an actual app. Google says it will be pushing users of the extension to try the app with a promo “over the next few weeks.”