A web search engine is a software system that is designed to search for information on the World Wide Web. The search results are generally presented in a line of results often referred to as search engine results pages (SERPs). The information may be a mix of web pages, images, and other types of files. Some search engines also mine data available in databases or open directories. Unlike web directories, which are maintained only by human editors, search engines also maintain real-time information by running an algorithm on a web crawler.

Google Search, commonly referred to as Google Web Search or just Google, is a web search engine owned by Google Inc. It is the most-used search engine on theWorld Wide Web, handling more than three billion searches each day. As of February 2015 it is the most used search engine in the US with 64.5% market share.

Bing (known previously as Live Search, Windows Live Search, and MSN Search) is a web search engine (advertised as a "decision engine") from Microsoft.Bing was unveiled by Microsoft CEO Steve Ballmer on May 28, 2009, at the All Things Digital conference in San Diego, California, for release on June 1, 2009. Notable changes include the listing of search suggestions while queries are entered and a list of related searches (called "Explore pane") based on[5] semantic technology fromPowerset, which Microsoft purchased in 2008.

Yahoo Search is a web search engine owned by Yahoo. As of February 2015 it is the third largest search engine in the US by the query volume at 12.8%, after its competitors Google at 64.5% and Bing at 19.8%.

Ask.com (originally known as Ask Jeeves) is a question answering-focused web search engine founded in 1995 by Garrett Gruener and David Warthen in Berkeley,California. The original software was implemented by Gary Chevsky from his own design. Warthen, Chevsky, Justin Grant, and others built the early AskJeeves.com website around that core engine. In late 2010, facing insurmountable competition from Google, the company outsourced its web search technology and returned to its roots as a question and answer site.[2] Douglas Leeds was elevated from president to CEO in 2010.

DuckDuckGo (DDG) is an Internet search engine that emphasizes protecting searchers' privacy and avoiding the filter bubble of personalized search results.[1]DuckDuckGo distinguishes itself from other search engines by not profiling its users and by deliberately showing all users the same search results for a given search term.[4] DuckDuckGo emphasizes getting information from the best sources rather than the most sources, generating its search results from key crowdsourced sites such as Wikipedia and from partnerships with other search engines like Yandex, Yahoo!, Bing, and Yummly