Each user has two to five instant messengers installed on the phone. All of them are used to one degree or another.

Over time, some messenger applications lose their leadership positions, giving way to new ones. So, in one year Skype moved from the first place, which it occupied for several years, to the fourth. Telegram is in fifth place. But it seems that this is also a temporary alignment, since the same Telegram is quickly conquering the market . In 2017, a new trend emerged — public channels and chats. Their presence attracts new users, in fact, turning messengers into social media. Perhaps this was the reason for the growth in popularity of Telegram.

Initially, messengers were created either as chats, for example conference calls, WhatsApp, or as an application for calls — Skype, Viber. Later, messengers began to add functions that were not originally there. So, in WhatsApp, the functions of audio calls were added, then video. Then there were open APIs, bots, masks, statuses, payment methods, public channels. However, it is difficult to introduce new functionality or change the structure when the messenger has millions of users. In the same WhatsApp, there are still no APIs and bots.

The main difficulty in creating an application for sending messages on Android or iOS is the development of the architecture. The structure of the application should be designed in such a way that new features can be added to it painlessly.