In its core search area, Web sites, Google said that it had increased the number of Web pages in its index to 4.28 billion, up from about 3 billion previously. Googles index of images has doubled in size to about 880 million images, said Peter Norvig, Googles director of search quality.
"Its a natural outgrowth of the growth of the Web and of us understanding better what pages are useful and which are not," Norvig said.
The Mountain View, Calif.-based companys index boost comes as its competitors build up their search engine arsenals.
Web site operators also reported this week a new Yahoo Inc. Web crawler indexing their sites and that Yahoo was using its own search technology, instead of Googles, for retrieving results. Yahoo officials have said that the company plans to switch from Google by the end of March.
However, in a statement, Google co-founder Larry Page trumpeted the increased size of Googles index.
"People worldwide can find more information with Google than with any other search engine," said Page, who is also the companys president of products
For its part, Google is continuing to extend beyond its core Web-page search. Along with doubling the size of its image index, the company also tweaked the user interface of its image search to make it easier for users to resize and view photos.
Google in the past few months also has been testing a service called Google Print, which lets users search the text of books to retrieve information such as chapters, reviews and bibliographic information. Google, which also will host pages for publishers, provides links to purchase the books, a spokesman said.
Rounding out Googles index are Usenet postings that appear on Google Groups. The number of postings included in the index has continued to rise, reaching about 845 million from 800 million previously, the company said.