The worldwide roll-out of Yahoo! Messenger with Voice came a day after Microsoft launched its new online messaging service with features such as internet telephony, group searching, and file and photo sharing.
While Yahoo! officials said the timing was a chance occurrence, the company is in an ongoing battle with Microsoft and Google for the loyalty of users whose website visits translate into revenues in the form of advertising dollars.
People can personalise the new IM service with plug-ins, mini-software applications that enable users to easily do web tasks such as check eBay auctions or scan a friend's wish-list at online retailer Amazon.com.
Terrell Karlsten, a Yahoo! spokeswoman, said that "it's a great way to find that perfect gift, or to learn what your friends are interested in".
"We collaborated closely with Amazon and eBay."
Yahoo! is in a battle with
Microsoft and Google for users
A "conversational plug-in" dubbed Event Finder enables those using the IM service to share maps in real time to collaborate about things such as meeting at a restaurant or going to the theatre.
"It's very interactive," Karlsten said.
Another plug-in lets Yahoo! IM users compare appointment calendars in real time as well as view their blog and photo webpages.
As of Tuesday, there were 100 plug-ins available worldwide to customise Yahoo!'s IM service, with options varying in different locations, according to Karlsten.
Yahoo! opened the IM platform so programmers anywhere could see how it works and improvise plug-ins that could be shared with the world.
"We want innovators and developers to make cool mini-applications for our Yahoo! Messenger users," Karlsten said.
"We want innovators and developers to make cool mini-applications for our Yahoo! Messenger users"
Among the enhancements built in by Yahoo! is the ability to pipe music or sound effects such as an audience booing or birds chirping into IM telephony on the internet.
Sunnyvale, California, based-Yahoo! also upped the size limit on file transfers by tenfold, to a gigabyte, to handle larger document and photos sent via IM.
Localised versions of Yahoo! Messenger with Voice were launched in Argentina, Australia, Brazil, Canada, China, France, Hong Kong, Korea, India, Italy, Germany, Mexico, Singapore, Spain, Taiwan, United Kingdom, and the United States.
Microsoft launched its new internet messaging service on Monday, touting it as the first in a barrage it is unleashing in the coming year in its battle for online devotees.
The new Windows Live Messenger gives IM users many of the functions previously limited to email.