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.