Zalo is the number-one IM app in Vietnam. It works very similarly to Viber and LINE: with it, you can send text messages and make calls using 3G or WiFi. Zalo works exactly as you would expect: You have to register using your phone number (although you can also install it on your tablet), and import your information from Facebook or Google Plus. That done, you can add contacts from the address list on your device. Although the main feature in Zalo is the ability to talk with your friends, the app also includes public chat rooms where you can meet strangers. These rooms are divided by category, so you can find one you like and chat with the people inside. Zalo is a powerful IM app whose greatest appeal lies in the number of active users it has in Vietnam.