Facebook WhatsApp is a FREE messaging and video calling app. It is used by over 2 billion people in more than 180 countries. It's simple, reliable, and private, so you can easily keep in touch with your friends and family. WhatsApp works on mobile and desktop devices even with slow connections, without subscription costs. Your personal messages and calls to friends and family are end-to-end encrypted. No one outside of your chats, not even WhatsApp, can read or listen to them.
Supported Android Devices : [4.0.3–4.0.4] Ice Cream Sandwich - [4.1–4.3.1] Jelly Bean - [4.4–4.4.4] KitKat - [5.0–5.0.2] Lollipop - [6.0 - 6.0.1] Marshmallow - [7.0 – 7.1.1] Nougat - [8.0-8.1] Oreo -  Pie