Windows Live Messenger will be "retired" in the first quarter of 2013 except in mainland China, Microsoft-owned Skype said in a blog post.
Windows Live Messenger is the world's most popular instant messaging choice with 40.6 percent of the installed base of IM programs, with Skype in second place at 27.39 percent.
Skype said it would assist Windows Live Messenger users during the coming months to help with the transition, the British online tech publication The Register reported Wednesday.
Beginning with Skype version 6.0 for Mac and Windows, users can sign into the service using a Microsoft account.
"Now users just need to update to the latest version of Skype, sign in using a Microsoft account, and their Messenger contacts will be there," Skype blogged.