In accordance with unofficial reports from last month, Google Allo instant messaging (IM) app started rolling out today and should be available for download worldwide by the end of the week. As Google has released its fair share of communication apps in recent years and there's still a lot of confusion about what exactly Allo is and how it works, here are the answers to all of those questions along with an explanation of what Allo can and cannot do (yet).
Google describes Allo as a "smart messaging app" which refers to some of the messenger's unique features which are explained below. However, don't let that confuse you as Allo is still an instant messaging app first and foremost. It was primarily designed for consumers, especially those who use Hangouts as Google is slowly turning that app into an enterprise tool similar to Slack. To use Allo, you need both a Google account and a phone number. Both of these are required for the app to make its intelligent predictions and facilitate the process of finding your friends, acquaintances, and colleagues on Allo. After signing in, you activate Allo just like most other IM apps which are tied to a phone number, i.e. you receive an authorization code via SMS.
While any phone number will do, note that the Play Store version of the app still doesn't support SIM-enabled tablets. That will hopefully change in the near future as Google already talked about iPad support so it makes sense for the app to also come to Android tablets. However, once that happens, you'll probably need a separate Allo account for your tablet as Allo currently doesn't support multiple devices and signing into the app on one phone signs you out of the last device you were using the app on. As for other devices, Allo hasn't yet been ported to desktops though you could theoretically use it on a Chromebook thanks to the Chrome OS Android support. Naturally, same restrictions still apply so you'll still only be able to log into Allo on a single device at any given time.
Furthermore, unlike some other popular IM solutions, Allo currently doesn't offer a way to make a backup of your chat history which is only stored locally. In other words, once you switch devices, you'll lose your chat history and only retain the group chat memberships which you had on the old device. That's definitely an inconvenience but Google is likely to add the backup option to Allo in the near future. As for phone number changes, the latest version of the app handles such scenarios pretty efficiently as you can unregister your phone number in the app's Settings menu which is especially useful when you're permanently changing numbers. However, note that this deletes all of your chat history and group chat memberships for good, though any Google Assistant history should still be preserved because it's technically tied your Google Account.