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Some users can get Duo video calls even if the app isn't installed
![Google Duo knock knock](https://www.androidauthority.com/wp-content/uploads/2016/05/Google-Duo-knock-knock.jpg)
- Some Android users can now receive Duo video calls without the app installed thanks to App Preview Messaging.
- App Preview Messaging allows messenger apps to display preview versions, which users can use to communicate.
- Allo has been using App Preview Messaging since it launched in 2016.
Google has experimented with allowing apps to be used even when they aren’t installed. The most popular example of this is Instant Apps—a web-based solution that loads apps as you access different parts of them. But, Google has another solution called App Preview Messaging. App Preview Messaging launched back in 2016 inside Google Play Services, letting users receive messages from certain apps without having those apps on their device. Allo has used it since launch, but now Duo has it too.
![send whatsapp message without saving contact siri shortcut running send whatsapp message without saving contact siri shortcut running](https://www.androidauthority.com/wp-content/uploads/2021/11/send-whatsapp-message-without-saving-contact-siri-shortcut-running.jpg)
Google seems to have flipped the switch in a recent update, as users without Duo can reportedly receive video calls. The calls start with the knock-knock (a video preview of who is calling) feature, just like they normally would. Users can answer, ignore, or mute the ringer just as they would with a regular voice call. If they decide to answer, users can chat and select which cameras to broadcast. A persistent notification shows up so they can return to the call if they go back to the home screen or another app. Google also gives users an easy way to block a person from video calling, because we all have that one friend.
The most significant drawback is that you can’t initiate calls without Duo installed. But, Google is betting that once you receive a Duo call, you’ll want to install the app for yourself. It’s a play that could increase Duo’s active users, even if it’s via a somewhat artificial method of acquisition.
If you do have Duo installed, there are only a select group of people that you can initiate a call with. iPhone, Windows Phone, and feature phone users are all out—this is for Android phones only. It also appears that not all Android users are eligible, but we’re not quite sure what disqualifies them.
Google promised when App Preview Messaging rolled out that it would move beyond Google apps. That doesn’t seem to have happened yet. There are a ton of messaging apps with their own platform that could benefit from this feature. Hopefully, Google lets them in on the fun soon too.