MOUNTAIN VIEW, Calif. - Google Inc. said late Monday it has agreed to acquire Urchin Software Corp., which makes software to help companies analyze the traffic at their Web sites.

Thousands of Internet sites use products from San Diego-based Urchin to help better understand their users' experiences and track the performance of advertisements and other aspects of visits to Web sites. Google expects the service will help Web sites increase their advertising returns.

Terms of the deal were not disclosed.

"This technology will be a valuable addition to Google's suite of advertising and publishing products," Jonathan Rosenberg, Google's vice president of product management said in a statement announcing the deal.

Mountain View-based Google said it anticipates the deal will close by the end of April.