Everyone can now make audio calls on Google's Duo.

Google rolled out audio calling in Duo last month, starting with users in Brazil. The feature lets you easily toggle between video or audio calls from within Duo's interface, and the app's technical lead Justin Uberti announced today that audio calling is now available to all users globally.

Google Duo audio calls

Just like Duo's video calls, the audio calls feature is optimized for spotty connections, so even if you're on a 2G cellular connection, you'll be able to make audio calls with passable clarity. The feature certainly makes the app much more versatile, but the main problem with Duo and Allo — an instant messaging app that has the Assistant baked in — is user adoption.

Both apps are aimed at emerging markets like India, where millions of users are making their way online for the first time. If Google launched them two or three years ago, they would've racked up millions of users. But with WhatsApp effectively sowing up the Indian market thanks to its smorgasbord of features and ubiquity across platforms — both Allo and Duo don't have a desktop app yet — there's little incentive for customers to install multiple apps when there's a single platform that does it all.