Data about web pages are stored in an index database for use in later queries. A query can be just a single word. The purpose of an index is to allow the needed information to be located as quickly as possible. When a person enters a query into a search engine (commonly by using key words), the engine determines its index and provides a listing of best-matching web pages, usually with a short summary containing the document’s title and often parts of the text. The advantage of a search engine depends on the relevance of the result set it gives back. While there may be millions of web pages that have a particular word or phrase, some pages may be more relevant, popular, or authoritative than others.

Blinkx was launched in 2004 and uses voice recognition and visual examination to process spidered video rather than rely on metadata alone. blinkx puts its collection at around 26,000,000 hours of content and claims to have the largest archive of video on the web.

CastTV is a Web-wide video search engine that was founded in 2006 and funded by Draper Fisher Jurvetson, Ron Conway, and Marc Andreessen.

Clipta is a deep crawling video search engine that indexes millions of videos from across the Internet. Clipta was founded and launched in 2008.

Dabble is a human powered video search engine indexing 29 million videos across hundreds of videos sites. Dabble launched in July, 2006. [Video search feature temporarily unavailable at Dabble.com]

Everyzing (formerly Podzinger until May, 2007) has spent $50 million building speech to text video search. Everyzing takes the user within the actual content by using speech recognition. This allows online video consumers to go directly to the point in the video for which they are searching.