There are already countless chatting software (such as WhatsApp, Skype, Discord, Facebook Messenger), but almost all of them are non-free software based on central servers, and their security and privacy are not guaranteed (any chat history of you will be sold to various companies). Many of them claim to encrypt communication content, even with end-to-end encryption, but when a platform is proprietary, there is simply no way for others to verify that it is as secure and private as it promises to be. Of course, there are some really safe and reliable ones, but they are frequently blocked by governments of various countries and cannot continue (such as Signal, Telegram).

Skype is currently the world's most popular free HD instant messaging software (and VoIP) for all kinds of desktop and mobile platforms. Low system resource requirement, high-quality voice communication and high stability have won its hundreds of millions of users around the world. After acquired by Microsoft in 2011, it became an independent department of Microsoft. And in 2013, if finally replaced Microsoft's own instant messaging tool MSN. In 2014, it released an embedded web version.