Update 9/22: According to the app's co-lead, Allo is now rolling out worldwide. At launch, it was geographically limited through the Google Play Store and iOS App Store.

Coming a month after the launch of Duo, Google's latest attempt at messaging is now available. The Google Assistant-infused Allo is rolling out on Android and iOS starting today with a full worldwide availability in the next few days.

Google "designed Allo to help you express yourself and keep the conversation going." Besides stickers from independent artists, the app allows messages, including emoji, to be sent in small (Whisper) or large text (Shout). Users can simply slide up and down on the send button to determine the size. A built-in drawing tool allows you to doodle on images before sending them.

Like in Inbox, Allo can suggest context appropriate Smart Reply for both text and images. They appear just under the last received message and can include emoji. Over time, the replies improve through machine learning and mimic how you normally express yourself in conversations.

The Google Assistant — available as a preview — is the marquee feature of Allo and can be brought up directly in any thread by typing "@google." It automatically suggest things like restaurant recommendations and bring up cards for both parties to browse. Additionally, there is an Assistant-specific thread that is essentially "Ok Google" with questions typed out and answers delivered through text.

Privacy and security-wise, there is an Incognito mode that encrypts chats end-to-end, uses discreet notifications, and has messages expire after a set time. Google notes that regular Allo chats are still encrypted.

Like Duo, Allo requires a phone number to register. Google notes that you can message those not using Allo through SMS or with app preview messages on Android. The app is available on the iOS App Store and still rolling out on the Play Store.