Google Duo

OS: Android

Google's new app, Duo, is a simple video-calling service that's available for Android and iOS today. Alongside the upcoming messaging app Allo, it's one of two communication apps Google announced earlier this year at its I/O conference, and one of four altogether from the company.

In a way, it's Google's answer to Apple's FaceTime, and it makes one-to-one calling between Android phones, and from Android to iPhone, very simple. Though both parties have to download the app to begin chatting (unlike FaceTime, which is baked into the dialer of compatible iPhones), it's still an intuitive app to use.

And while Android users will likely enjoy using Duo to video-call all their friends, iPhone owners won't find it compelling enough to ring up fellow iPhone users. However, it may certainly become their go-to app when calling up a buddy who uses Android. With that said, here are its main highlights:

You'll see previews with Knock Knock

Duo's unique feature is Knock Knock, which gives you a preview of who is calling by firing up the camera on the other end of the line. If you're initiating the call, you'll see a little notice that says your video is visible, which means the other person can see what you're doing right at that moment in real time. Android users can see Knock Knock regardless of whether Duo is opened or not (like on the lock screen). On the iPhone though, you'll only see it if you're in the app. Otherwise, you'll just get a little notification saying someone's calling you.

Google's rationale for this is that Knock Knock already gets you smiling before the call starts. Of course, that's assuming you actually like/want to speak to the other person who is on the other line. Seeing family members on the other line? That gets me smiling. Seeing the face of my boss? Mmm, not so much (see below). Editor's Note from said boss: "Hmph."

You can disable Knock Knock

Before you worry about seeing anything you don't want to see from the other line, know that you can only receive Knock Knocks from people who are already in your contact list. You can also block individual people from calling you. (By the way, when you block a person on Duo, the person won't know it. When they call, they'll just hear your line ring and ring continuously.)

If Knock Knock really isn't your thing, you can disable it altogether in Duo's Settings menu. You can't disable Knock Knock on a person-to-person basis though, so it's Knock Knock or nothing.

Its interface is super simple

Duo has an incredibly user-friendly and intuitive interface. Before you begin a call, you'll see icons to start a video call and your recent contacts (sorry, there's no audio-only option). During a call, you'll see yourself (in a small little circle), and icons to mute audio, switch cameras and hang up. Video from the other line fills up your screen and that's pretty much it. If you'd rather have your camera fill up the screen (for example, you're touring a house to the person on the other line), just tap the preview circle and your view will switch. Read more about getting started with Duo.

It's different than Hangouts (no, really)

At this point you might be wondering what makes Duo different than Google's other video-calling service, Hangouts, and you're not alone if you think the company has one too many communication tools. But according to Google, Duo is supposed to be way more specialized. Whereas Hangouts can be used on desktops, supports messaging and group chats, and has multiway video for collaboration (and its interface reflects these extra features), Duo does one thing and one thing only: video calls on your phone or tablet.

Unlike Hangouts, it reaches people through their phone numbers, not their Gmail. Other than downloading the app, you won't have to force anyone to log into their Google accounts or sign up for a new service. And the best difference between it and Hangouts? It uses end-to-end encryption, so your data can't be viewed from third parties or even Google itself.

It works only as well as your connection

Not surprisingly, if you have a good Wi-Fi or data connection, the app works smoothly. When I used it and had strong coverage, people looked clear and their voices were easy to understand. I experienced some lag from time to time, but it usually lasted just a few seconds.

When one of my colleagues was on a weaker Wi-Fi network, however, he was extremely pixelated. Though audio came in clear, his face just ended up looking like a study in 1880s pointillism. After he switched to a stronger Wi-Fi network, however, his image cleared up and our conversation was stable.

You might actually want to use it

There are loads of apps these days that either center around video chatting or have it as one of their features. Duo is coming into a crowded industry, competing not only against Skype, Facebook Messenger and others, but even Google itself with Hangouts.

All three of these competing apps do much more than simply one-to-one video calls. For example, they support messaging and you can start video calls with multiple people. Plus, with Messenger, you don't need a Facebook account (a phone number will suffice).

But Google didn't create Duo to be an all-in-one communication platform; to do so would make it hairier to use. Google also believes that when a person decides to video-call a friend, one rarely wants to pivot to messaging or group chatting anyway.

Because Duo offers just the bare bones, it can provide a solid, no-muss-no-fuss video calling service. This singular functionality frees you from having to sign in another account, make sure your buddy has the same service or take time to navigate through a busy interface. Plus, its end-to-end encryption means your conversations are protected from prying eyes. (As I mentioned before, Hangouts doesn't have that and Skype isn't secure either. Messenger has begun testing end-to-end user privacy, but hasn't rolled it out en masse.)

True, iPhone users will probably keep using FaceTime to communicate with one another, but Duo bridges the gap between iOS and Android. With its quirky Knock Knock feature, simplistic approach and data encryption, Duo makes it a whole lot easier to say hi and wave hello.