Microsoft and Yahoo! will allow users of their respective IM chat services to communicate with each other without recourse to a third-party client, such as Trillian, according to a report. Neither company would confirm the story to the Wall Street Journal.

Microsoft and Yahoo! hold 44 per cent of the worldwide IM user base between them, with AOL taking the lion's share of 56 per cent, according to Radicati Group. Third parties such as Jabber aren't statistically significant, with Google's Jabber-based chat holding just 0.5 per cent, and apparently irc doesn't count.

The IM service operators have pledged to improve interoperability for the general consumer for many years. However, the efforts have only borne fruit in the enterprise space. AOL has solemnly vowed to improve interoperability twice: once in a promise to the FCC after the Time Warner merger, and again as a result of the 2003 agreement which settled its differences with Microsoft. Nothing came of either pledge.

These days all the major players regard IM clients as a vehicle for voice communication, typically at the expense of adding inter-network interoperability. AOL and Yahoo! both introduced PC-to-PC calling in late 1999 and Microsoft followed suit in MSN Messenger the following year. But the spread of broadband has seen VoIP services like Skype and Vonage gain a strong following, and neither of the established players want to cede the desktop space to new challengers.

While the technical challenge of agreeing protocols is trivial, harmonizing the respective smiley sets could provide a challenge. Wink-dash-bracket. ®