WhatsApp. I have been using WhatsApp from last 1year. Some other chatting apps there in market but most popular is WhatsApp.
The service provide by WhatsApp is good. It is very fast and user-friendly app. It has service all over world so I can chat with my friends who are staying in aboard.
The what's app providing huge collections of smiles and emotional icons. I often use WhatsApp to make call to my friends. If there 3g network the quality of call is good no any voice break. 2g network not support that much good quality for call but you can make chat.
The uploading and downloading image or audio is super fast. It has image zoom facility and I can clear the conversation history by selecting weekly or monthly option. The user interface of WhatsApp is awesome it feels good when you open app. It upgraded version they added more service and they are not changing for using app. Most good thing about app is they not giving any advertisement so it feels good. It has unique privacy settings like who can see profile pic and block number etc. Some other most popular app are hike
