WhatsApp is extremely popular in Russia, Brazil, Mexico, India, Spain, Italy and Germany, and amongst the geographically dispersed migrants from those countries. One of the driving forces for the popularity of WhatsApp is that it is often significantly cheaper to send messages via a data plan (or wifi) than it is to pay the excessive rates that some countries charge for sending messages via SMS. WhatsApp does not support third-party clients or chatbots.
It has been repeatedly blocked in Brazil by court order. In Brazil, WhatsApp is used as a popular form of social media: a lot of people use WhatsApp for large group messages to distribute links, memes and videos, many of which are political or social in nature. The blocking of WhatsApp in Brazil is more blocking a "broadcast" social networking site like Twitter than it is like that of a person-to-person messaging service.
WhatsApp Web client
WhatsApp has a desktop/web client. Due to the way end-to-end encryption is implemented in WhatsApp, this is not a true fully-fledged client. All messages sent using the web client are sent first to the user's phone and then sent on from there. It does not work without the mobile client. This means that it won't work if your phone has run out of battery or you wish to access your WhatsApp messages in a country where you do not have mobile service.
The afterthought feeling of the web client is in part because WhatsApp has found most of its popularity amongst users, and in countries, where PC ownership is low compared to smartphone use.
WhatsApp blocked in Brazil for ~1 day (of original 72 hour order).
WhatsApp was blocked in Brazil for ~12 hours (of original 48 hour order).
- 2015-01-21 Andre Garzia: WhatsApp doesn't understand the web
- Whatsapp blocks links to rivaling messenger telegram: 
- 2015-07 WhatsApp, Instagram and Facebook account of third-party WhatsApp API developer blocked 
- 2014-02-20 You May Not Use WhatsApp, But the Rest of the World Sure Does, Wired News