Plaxo is an online address book service founded by Napster co-founder Sean Parker, Minh Nguyen, and two Stanford engineering students, Todd Masonis and Cameron Ring.

Plaxo provides automatic updating of contact information. Users and their contacts store their information on Plaxo's servers. When this information is edited by the user, the changes appear in the address books of all those who listed the account changer in their own books. Once contacts are stored in the central location, it is possible to list connections between contacts and access the address book from anywhere. The major address books supported appear to be Outlook/Outlook Express, Mozilla Thunderbird, and Mac OS X Address Book,[1] though other ones can be supported through an application programming interface. [2]

Plaxo, based in Mountain View, California, is currently privately held and supported by venture capital. In March 2006, the website reported 10 million users. [3]

On July 7, 2005, Plaxo announced it had struck a deal with America Online to integrate its contact management service with its AOL and AIM products. [4]

Plaxo has faced criticism from people who were upset about receiving a number of requests from Plaxo users to update their contact information, and who wondered how the company was planning to make money from a free service that collects personal contact and network information. The company's official response to these issues can be found at [5].

• Plaxo
• Plaxo company blog