Google said back in December that the messaging service Google Allo would be shut down at some point in March, and a banner across the official Allo website has confirmed that March 12th, 2019, was its last day in operation.
A message on the home page is saying
“Allo is signing off.
Learn how to export your chats and more.
We’re saying good–bye to Allo in March, 2019. During our time together, we brought you a smarter way to chat, with features like the Google Assistant, Allo for web and selfie stickers. We’re working to bring your favorite features to the Messages app so you can have richer conversations with all your friends. If you have an Android phone, we hope you’ll try Messages!”