Microsoft will discontinue publication of its MSN Encarta online reference site and related software products later this year, according to a notice quietly posted on the site, as spotted by Emil Protalinksi of Ars Technica. The decision comes after years of competition with Wikipedia, the popular online encyclopedia that relies on the contributions of experts and other users for its material.

"Encarta has been a popular product around the world for many years," the official notice says. "However, the category of traditional encyclopedias and reference material has changed. People today seek and consume information in considerably different ways than in years past. As part of Microsoft’s goal to deliver the most effective and engaging resources for today’s consumer, it has made the decision to exit the Encarta business."

The decision takes effect Oct. 31 for most Encarta sites around the world, and on Dec. 31 in Japan. The company says it will stop selling Encarta software products in June. I've asked Microsoft how many jobs will be affected, among other details, and I'll update this post depending on the response.

For a story about Encarta five years ago, I spoke with Wikipedia founder Jimmy Wales. "Clearly it's difficult to sell something in a shrink-wrapped box if something far superior is available for free on the Web," he said at the time. He also predicted -- presciently, as it turns out -- that it would become "harder and harder" for Encarta to find an audience.

Update: What should Microsoft do with mothballed Encarta content?