Yahoo on Monday unveiled a major expansion to its Web search index, which now scours more than 20 billion objects across the Internet. The number trumps search leader Google's 11.8 billion-item index, although Yahoo admits that when it comes to Web searches, size doesn't matter most.

"While we typically don't disclose size (since we've always said that size is only one dimension of the quality of a search engine), for those who are curious this update includes just over 19.2 billion web documents, 1.6 billion images, and over 50 million audio and video files," developer Tim Mayer wrote in the Yahoo! Search blog.

Google responded to the news by saying it has yet to notice any substantial change to Yahoo's index via its search results. And Yahoo concedes that the increase in data will take time to appear.

"Note that as with all index updates we are still tuning things so you'll continue to see some fluctuation in ranking over the next few weeks. Ensuring you find what you're looking for is the true measure of search engine quality and something we strive for every day."

Nonetheless, Yahoo has earned bragging rights as the largest search engine for the first time. The company had previously remained mum on its index size, while Google openly boasts its numbers below search results.

Yahoo actually utilized Google for its search until early last year, when it launched its own homegrown engine. Microsoft's MSN unit followed suit and both companies plan to launch targeted text advertising to compete with Google's popular AdWords program.