Baidu Inc, simply known as Baidu and incorporated on January 18, 2000, is a Chinese web services company headquartered in the Baidu Campus in Beijing's Haidian district.

Baidu offers many services, including a Chinese language search engine for websites, audio files, and images. Baidu offers 57 search and community services including Baidu Baike, an online collaboratively built encyclopedia, and a searchable keyword-based discussion forum.

Baidu was established in 2000 by co-founders, Robin Li and Eric Xu. Both of the co-founders are PRC nationals who studied and worked overseas before returning to China. In June 2011, Baidu was ranked 5th overall in the Alexa Internet rankings. During the fourth quarter of 2010, it was estimated that there were 4.02 billion search queries in China of which Baidu had a market share of 56.6 percent.China's internet-search revenue share in the second quarter 2011 by Baidu was 76 percent. In December 2007, Baidu became the first Chinese company to be included in the NASDAQ-100 index.

Baidu provides an index of over 740 million web pages, 80 million images, and 10 million multimedia files. Baidu offers multimedia content including MP3 music and movies, and is the first in China to offer Wireless Application Protocol (WAP) and personal digital assistant (PDA) based mobile search.

The name "Baidu" is a quote from the last line of Xin Qiji's classical poem "Green Jade Table in The Lantern Festival" saying: "Having searched for her hundreds and thousands of times in the crowd, suddenly turning back by chance, I find her there in the dimmest candlelight."

Development In 1994, Robin Li joined IDD Information Services, in New Jersey vision of Dow Jones and Company, where he helped develop a software program for the online edition of The Wall Street Journal. He also did work on better algorithms for search engines and remained at IDD Information Services from May 1994 to June 1997.

In 1996, while at IDD, Li developed the RankDex site-scoring algorithm for search engines results page ranking and received a US patent for the technology. He later used this technology for the Baidu search engine.

Services Baidu offers several functions to locate information, products and services using Chinese-language search terms, such as, search by Chinese phonetics, advanced search, snapshots, spell checker, stock quotes, news, knows, postbar, images, video and space information, and weather, train and flight schedules and other local information. The user-agent string of Baidu search engine is baiduspider. A Baidu application for Apple's IOS is also available.