• by Shankar Gupta , July 13, 2006

In a challenge to AOL's popular instant messenger service, the second and third most popular services, Microsoft's Windows Live Messenger and Yahoo Messenger, today launched a closed beta test of a merger of their two networks.

The new compatbility, first announced last October, will allow users of the separate services to message each other without changing platforms.

The interoperability, which is rolling out about two weeks behind schedule, will be available in the United States and 18 other markets, including the United Kingdom, Germany, France, Korea, Hong Kong, and India. In addition to enabling users to send instant messages to each other, the service allows them to view the status of messages, share selected emoticons, view offline messages, and add new contacts across services.

Combined, the two networks appear to have a better opportunity to compete with AOL, the current instant messaging leader, as well as with Google's nascent service, launched last year. AOL Instant Messenger garnered 47 million unique users last month, while MSN claimed 28 million and Yahoo drew 22 million, according to Nielsen//NetRatings. Combined, MSN and Yahoo have 43 million unduplicated unique users.