The Deja News Research Service was an archive of messages posted to Usenet discussion groups, started in 1995 by Steve Madere in Austin, Texas. Its powerful search engine capabilities won the service acclaim, generated controversy, and significantly changed the perceived nature of online discussion.

The Deja News logo as it appeared in 1997.

While archives of Usenet discussions had been kept for as long as the medium existed, Deja News offered a novel combination of features. It was available to the general public, provided a simple World Wide Web user interface, allowed searches across all archived newsgroups, returned immediate results, and retained messages indefinitely. The search facilities transformed Usenet from a loosely organized and ephemeral communication tool into a valued information repository. The archive's relative permanence, combined with the ability to search messages by author, raised concerns about privacy and confirmed oft-repeated past admonishments that posters should be cautious in discussing themselves and others. (Von Rospach)

While Madere was initially reluctant to remove archived material, protests from users and legal pressure led to the introduction of "nuking," a method for posters to permanently remove their own messages from search results. It already supported the use of an "X-No-Archive" message header, which if present would cause an article to be omitted from the archive. This did not prevent others from quoting the material in a later message and causing it to be stored. Copyright holders were also allowed to have material removed from the archive. According to Humphrey Marr of Deja News, copyright actions most frequently came from the Church of Scientology.

The deja.com logo used from 1999.

The service was eventually expanded beyond search. My Deja News offered the ability to read Usenet in the traditional chronological, per-group manner, and to post new messages to the network. Deja Communities were private Internet forums offered primarily to businesses. In 1999 the site (now known as Deja.com) sharply changed direction and made its primary feature a shopping comparison service. During this transition, which involved relocation of the servers, many older messages in the Usenet archive became unavailable.

By late 2000 the company, in financial distress, sold the shopping service to eBay, who incorporated the technology into their half.com service. By 2001 the search service was shut down. The archives were acquired by Google and reintroduced as Google Groups. Archive coverage was extended back to 1981 with the addition of collections from private sources. Longtime users sometimes refer to the resurrected archive as "Dejagoogle" or "Gooja."

• Chuq Von Rospach. A Primer on How to Work With the Usenet Community. Usenet introductory document posted regularly until 1999.
• George Lawton (January 1997). Internet archives: Who's doing it? And can you protect your privacy?. SunWorld.
• Andy Langer (July 14,1997). The Post Man Always Saves Twice. Austin Chronicle.
• Courtney Macavinta, Janet Kornblum (December 8, 1997) Deja News joins antispam war. C|Net news.com.
• Greg R. Notess (July 1998). On The Net: DejaNews and Other Usenet Search Tools ONLINE magazine.
• Janelle Brown (May 24, 1999). What does it take to make a buck off of Usenet? Salon.
• Hulk Snead (November 27, 2000). Geekquake, or, I Hear America Whining. Suck.
• Ryan Naraine (December 12, 2000). eBay Acquires Deja.com's Technology. internetnews.com (Jupiter Media).
• Google Inc. (February 12, 2001). Google Acquires Usenet Discussion Service and Significant Assets from Deja.com. Press release.