What was the name of the predecessor to Wikipedia?

The predecessor to Wikipedia was Nupedia. It was an online encyclopedia founded by Jimmy Wales and supported by Bomis, with Larry Sanger serving as editor-in-chief during its most important early period.

Nupedia launched on 9 March 2000 and aimed to produce carefully reviewed reference articles. Unlike Wikipedia, it was not a wiki: articles passed through a demanding seven-stage process involving assignment, expert review, open review, copyediting and final approval. Contributors were generally expected to have relevant subject knowledge, and the project emphasized editorial quality.

In January 2001, Nupedia began Wikipedia as a side project. The wiki format allowed volunteers to create and revise articles far more quickly, without waiting for Nupedia’s lengthy review process. Wikipedia grew rapidly and soon overshadowed its parent project. Nupedia’s server went offline in September 2003, and its remaining encyclopedic content was absorbed into Wikipedia.

Citizendium is sometimes confused with Nupedia because Larry Sanger later founded it as another expert-oriented encyclopedia. Citizendium came later, however; it was not Wikipedia’s predecessor.