Microsoft has announced that recently-acquired Skype will replace its Messenger online chat service.
"Skype and Messenger are coming together," Skype said in a post at its website.
"By updating to Skype, Messenger users can instant message and video call their Messenger friends."
The transition began a few weeks ago with the release of Skype 6.0 software that lets people sign into the online communication service using Microsoft accounts.
"We want to focus our efforts on making things simpler for our users, while continuously improving the overall experience," Skype said.
Messenger will "retire" in every country but China in the first quarter of next year.
Skype features include video calls and being able to call mobile phones from computers, as well as being able to connect with friends at leading social network Facebook.
Early this year, Microsoft's Skype division chief Tony Bates cited Facebook as key to the growth of the service, which hoped to quadruple its number of users to a billion.
A Skype feature on Facebook allows for multiperson conversations and a camera icon that can be clicked on for instant one-on-one video calls with friends.
Skype, which bypasses the standard telephone network by channelling voice and video calls over the web, allows users to make low-cost or free phone calls over the internet using their computers or smartphones.
Microsoft last year bought Skype for $US8.5 billion ($A8.24 billion) in a move seen as aimed at boosting its presence in an online arena dominated by Google and Facebook.
Skype was founded in 2003 and acquired by online auction giant eBay in September 2005. It was sold to an investment group led by Silver Lake in November 2009 in a deal that valued the company at $US2.75 billion.