Messenger 9.0 features what Yahoo calls an "in-line player" that enables users to send URLs to each other and then watch video and flip through photos together, while communicating over IM or an Internet phone connection.
"We've punched up Yahoo Messenger to make keeping in touch with friends and family even more fun, with features like the in-line media player that helps people easily share their favorite videos, images, and photos right in the IM window," Sabrina Ellis, VP of Yahoo Messenger, said in a statement.
In addition, the "friends list" on the new version has been redesigned with more space that makes it easier to see a contact's photo and status and to connect by instant messages, voice over IP, or text messaging to a mobile phone.
The upgrade also includes call forwarding, so Internet telephony calls to Messenger can be sent to a mobile phone or landline as a voice mail. In addition, users can send an unlimited number of attachments, with a file size limit of up to 2 Gbytes, and photo sets from Yahoo's Flickr picture service can be shared in real time.
The service includes automatic antivirus scanning, an important feature given that Messenger is vulnerable to attacks from virus writers and hackers.
Yahoo Messenger has 94.3 million users worldwide, according to Yahoo. Along with the upgrade, localized versions of Messenger have been released in six new markets: India, Indonesia, Malaysia, Philippines, Thailand, and Vietnam. The additions bring the total number to 25.