Google Duo (for iPhone)

By Max Eddy

In a rare move, Google recently unleashed its Duo video chat app simultaneously on Android and iOS. Duo is intended to make video chatting easier and more accessible than ever. While some of its features are clever, Duo isn't tightly integrated enough with Apple or Google and is more limited as an iPhone app than on Android. It just can't compete with Apple's excellent FaceTime service and Facebook Messenger (both of which are Editors' Choice winners) or Google's own Hangouts.

Face To Face
Google announced Duo at this year's Google I/O conference, along with Google Home, an Amazon Echo competitor, and Allo, a text chatting app that bakes in the new Google Assistant bot. Duo is the only product to have yet seen the light of day, however.

While the Android app works on devices running operating system versions as old as 4.1, the iPhone version only works on iOS 9 or later—then again, that's most iPhones. It's compatible with all current iOS devices, and I had no trouble installing it on my iPhone 6.

Speak to Me
The iPhone version is effectively identical to the Duo Android app, which I've reviewed separately. I'll run through the basics here, though, and I'll also talk about the iOS-specific aspects of Duo. Getting started requires approving the privacy permissions for access to the camera, contacts, and notifications. You confirm your phone number by responding to a text message. The service scours your Contacts list and matches you against other Duo users—there is no way to manually input numbers. The interface is simple yet elegant, and I especially like the smooth animations when switching between a full-screen view through my camera and a full screen view of the caller's camera. Toggling front- and rear-facing cameras is also a cinch.

Duo's killer feature is Knock Knock. When someone calls with Duo, the app turns on the caller's video camera (but not the microphone) and displays a live feed to the recipient. Think of it as looking through a peephole to see who's knocking—hence the name. It's an excellent idea, but its implementation is a bit troublesome. For one thing, callers are informed that their cameras are on, but recipients aren't told that their cameras are off. I could easily see recipients, in particular, being confused, and perhaps mistakenly believing that their camera is also on, without their permission.

More problematic is how Knock Knock works on the iPhone. If your phone is unlocked—that is, the screen is on and you've already entered your passcode or scanned you fingerprint—the Knock Knock call screen will fill your view and you can answer or decline the call, just as on Android. But if your phone is locked, as is more often the case, you only see a notification on the lock screen. The phone rings and vibrates, but swiping on the notification automatically accepts the call. I'd rather see swiping activate Knock Knock. This happens because Apple doesn't allow apps to take over the lock screen. That might change after iOS 10, when Apple will launch a new VoIP API for developers. We'll see if Google can take advantage of it for Duo when it's available.

Also, you can only accept a call, not reject it, from the lock screen. If your phone is unlocked, you can accept or reject the call, but you can't send a text message declining the call, for example. Other apps, like Snapchat, provide many more options, such as responding with a text message, opening an audio-only channel, or creating a text chat. Duo is designed to be simple, but this behavior seems too limiting.

Gotta Get That Buy-In
The biggest problem with Duo, however, is that it requires whomever you wish to call to also install Duo. FaceTime, a video calling app from Apple, is installed on all iOS devices by default. There's also FaceTime for OS X computers, which is interoperable with the mobile version. Duo has no desktop version, and therefore offers no calling between desktops and mobile devices.

Google Hangouts, on the other hand, is closely associated with users' Google accounts. There's virtually no signup, since most everyone has a Google account, and Hangout messages can be received on several different platforms. Facebook Messenger will also let you send messages to other Facebook users that haven't signed up for Messenger but are on Facebook. Viber is also worth mentioning, because its best feature is the ability to move a call between mobile and desktop devices easily, something else Duo cannot do.

Testing, Testing
Google claims that Duo will function well in even poor network environments. The app does have settings that let it hand off calls between Wi-Fi and cellular networks, but in my testing this feature was spotty at best. Calls took several seconds, or sometimes multiple attempts to connect. This was while connected via Wi-Fi with a fast FiOS connection, which we consider to be a best-case Wi-Fi scenario. Interestingly, my Nexus 5X seemed to have an easier time making and receiving Duo calls than my iPhone.

I also tested Google Duo over cellular and was very surprised to find that calls connected much faster and more reliably than over Wi-Fi. I recommend making Google Duo calls when you have both cellular and Wi-Fi connectivity available.

It's also worth noting that Duo is only for one-to-one video calls. If you'd like to get multiple people involved, Google Hangouts or Skype are better choices.

Can You See Me?
Google says that Duo calls are encrypted end-to-end, which is good, but the company has shared few other details and does not disclose how calls are encrypted and what protocols are used. Certain messages in Allo, Google says, will be secured with the open-source Signal protocol. The Signal protocol has been picked over by the open-source community, and has been used to secure VoIP and text messages in the Signal app, WhatsApp, and the latest version of Facebook Messenger. These are exactly the kinds of details I'd like to know about Duo's encryption.

I give credit to Google for including a blocking feature in Duo. It's available from the Settings menu, and it lets you blacklist contacts from whom you no longer wish to receive calls. However, I'd like the block function to be available from the call screen and during calls as well.

Do You Duo?
Duo is a simple, elegantly designed app that succeeds in making video chat easy. The Knock Knock feature is smart, and, while it needs tweaking, I can easily see it becoming an industry standard. However, because Duo lacks close integration with other Google services and requires a separate download and setup, I doubt the app itself will ever become ubiquitous enough to be really useful. This is especially true on iPhones, where FaceTime is tightly wound into the OS, and where excellent third-party options like Facebook Messenger and, ironically, Google Hangouts are already available. Google Duo is interesting and it won't cost you anything to try it, but unless your friends are on it or are likely to join, it's not a must-download app.