DuckDuckGo ( DDG ) is an Internet search engine that emphasizes protecting searchers' privacy and avoiding the filter bubble of personalized search results.  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,  and emphasizes returning the best results, rather than the most results, generating those results from over 400 individual sources, including crowdsourced sites such as Wikipedia, and other search engines like Bing, Yahoo!, and Yandex.   In November 2018, it had 29,661,659daily direct searches on average. 
Some of DuckDuckGo's source code is free software hosted at GitHub under the Apache 2.0 License,  but the core is proprietary. The company registered the domain names ddg .gg on February 22, 2011, and ddg.co on September 20, 2013, which are used as shortened URL aliases that redirect to duckduckgo.com .
On September 18, 2014, Apple included DuckDuckGo in its Safari browser as an optional search engine.   On November 10, 2014, Mozilla added DuckDuckGo as a search option to Firefox 33.1.  On May 30, 2016, The Tor Project, Inc made DuckDuckGo the default search engine for Tor Browser 6.0.   
DuckDuckGo's results are a compilation of "over 400" sources, including Yahoo! Search BOSS ; Wikipedia ; Wolfram Alpha ; Bing ; its own Web crawler (the DuckDuckBot ); and others.   It also uses data from crowdsourced sites, including Wikipedia, to populate "Zero-click Info" boxes – grey boxes above the results that display topic summaries and related topics.
Weinberg has refined the quality of his search engine results by deleting search results for companies he believes are content mills , like Demand Media's eHow, which publishes 4000 articles per day produced by paid freelance writers, which Weinberg says is, "...low-quality content designed specifically to rank highly in Google's search index." DuckDuckGo also filters pages with substantial advertising. 
In addition to the indexed search results, DuckDuckGo displays relevant results, called Instant Answers, on top of the search page. These Instant Answers are collected from either 3rd party APIs or static data sources like text files. The Instant Answers are called zeroclickinfo because the intention behind these is to provide what the user is searching for on the search result page itself so that the user does not have to click any results to find what they are looking for. As of August 9, 2018, there are 1231 Instant Answers active. 
The Instant Answers are open source  and are maintained on GitHub, where anyone can build or work on them.
Tor hidden service
DuckDuckGo includes "!Bang" keywords, which give users the ability to search on specific third-party websites – using the site's own search engine if applicable. As of October 2018, 11,414 "bangs" for a diverse range of Internet sites are available.  In December of 2018 around 2,000 "bangs" were deleted. Some of them were deleted due to being broken, while others, such as searches of pirated content sites, were deleted due to liability reasons. 
DuckDuckGo earns revenue by serving ads from the Yahoo–Bing search alliance network, and through affiliate relationships with Amazon and eBay. 
DuckDuckGo was founded by Gabriel Weinberg on February 29, 2008 in Valley Forge, Pennsylvania.  Weinberg is an entrepreneur who previously launched Names Database, a now-defunct social network. Initially self-funded by Weinberg, DuckDuckGo is advertising -supported, but the user has the option to disable ads.  The search engine is written in Perl and runs on nginx, FreeBSD, and Linux.   DuckDuckGo is built primarily upon search APIs from various vendors. Because of this, TechCrunch characterized the service as a "hybrid" search engine.   Weinberg explained the beginnings of the name with respect to the children's game duck, duck, goose. He said of the origin of the name: "Really it just popped in my head one day and I just liked it. It is certainly influenced/derived from duck duck goose, but other than that there is no relation, e.g., a metaphor."  DuckDuckGo was featured on TechCrunch's Elevator Pitch Friday in 2008,  and it was a finalist in the 2008 BOSS Mashable Challenge. 
In July 2010, Weinberg started a DuckDuckGo community website (duck.co) to allow the public to report problems, discuss means of spreading the use of the search engine, request features, and discuss open sourcing the code.
DuckDuckGo was self-funded until Union Square Ventures and angel investors invested in DuckDuckGo in October 2011. Union Square partner Brad Burnham stated, "We invested in DuckDuckGo because we became convinced that it was not only possible to change the basis of competition in search, it was time to do it."   In addition, Trisquel, Linux Mint, and the Midori web browser switched to use DuckDuckGo as their default search engine. 
By May 2012, the search engine was attracting 1.5 million searches a day. Weinberg reported that it had earned US$115,000 in revenue in 2011 and had three employees, plus a small number of contractors.  Compete.com estimated 266,465 unique visitors to the site in February 2012.  On April 12, 2011, Alexa reported a 3-month growth rate of 51%.  DuckDuckGo's own traffic statistics show that in August 2012 there were 1,393,644 visits per day, up from an average of 39,406 visits per day in April 2010 (the earliest data available).  In a lengthy profile in November 2012, The Washington Post indicated that searches on DuckDuckGo numbered up to 45,000,000 per month in October 2012. The article concluded: "Weinberg's non-ambitious goals make him a particularly odd and dangerous competitor online. He can do almost everything that Google or Bing can't because it could damage their business models, and if users figure out that they like the DuckDuckGo way better, Weinberg could damage the big boys without even really trying. It's asymmetrical digital warfare, and his backers at Union Square Ventures say Google is vulnerable." 
At its keynote speech at WWDC 2014, Apple announced that DuckDuckGo would be included as an option for search on both iOS 8 and OS X Yosemite.  On March 10, the Pale Moon web browser, starting with version 24.4.0, included DuckDuckGo as its default search engine, as well as listed it on the browser's homepage.  In May 2014, DuckDuckGo released a redesigned version to beta testers through DuckDuckHack.  On 21 May 2014, DuckDuckGo officially released the redesigned version that focused on smarter answers and a more refined look. The new version added many new features such as images, local search, auto-suggest, weather, recipes, and more. 
In July 2016, DuckDuckGo officially announced the extension of its partnership with Yahoo! that brought new features to all users of the search engine, including date filtering of results and additional site links. It also partners with Bing, Yandex, and Wikipedia to produce results or make use of features offered. The company also confirmed that it does not share user information with partner companies, as has always been its policy.  
On January 23, 2018, DuckDuckGo revamped its browser extension and mobile app in an effort to keep internet users safe “beyond the search box”. The revamped extension and app include a tool for rating websites based on their use of encryption and ad tracking networks as well as the ability to block ad tracking networks. The extension also provides Terms of service summaries from Terms of Service; Didn't Read. 
It feels a lot like early Google, with a stripped-down home page. Just as In-N-Out doesn't have lattes or Asian salads or sundaes or scrambled eggs, DDG doesn't try to do news or blogs or books or images. There's no auto-completion or instant results. It just offers core Web search—mostly the "ten blue links" approach that's still really useful, no matter what its critics say ... As for the quality, I'm not saying that Weinberg has figured out a way to return more relevant results than Google's mighty search team. But DuckDuckGo ... is really good at bringing back useful sites. It all feels meaty and straightforward and filler-free ... 
The barebones approach cited in his quote have since changed; DuckDuckGo now has auto-completion and instant results for example. McCracken included the site in Time' s list of "50 Best Websites of 2011". 
Thom Holwerda, who reviewed the search engine for OSNews , praised its privacy features and shortcuts to site-specific searches as well as criticizing Google for "track[ing] pretty much everything you do", particularly because of the risk of such information being subject to a U.S. government subpoena.  In 2012, in response to accusations that it was a monopoly, Google identified DuckDuckGo as a competitor. Weinberg was reportedly "pleased and entertained" by that acknowledgment. 
483 days to get 2M searches,
and then just 8 days to pass 3M searches:
In June 2013, DuckDuckGo indicated that it had seen a significant traffic increase; according to the website's Twitter account, on Monday, June 17, 2013, it had three million daily direct searches. On average during May 2013, it had 1.8 million daily direct searches. Some  relate this claim to the exposure of PRISM and to the fact that other programs operated by the National Security Agency (NSA) were leaked by Edward Snowden. Danny Sullivan wrote on Search Engine Land that despite the search engine's growth "it's not grown anywhere near the amount to reflect any substantial or even mildly notable switching by the searching public" for reasons due to privacy, and he concluded "No One Cares About "Private" Search".  In response, Caleb Garling of the San Francisco Chronicle argued: "I think this thesis suffers from a few key failures in logic" because a traffic increase had occurred and because there was a lack of widespread awareness of the existence of DuckDuckGo.  Later in September 2013, the search engine hit 4 million searches per day.   
As of November 2018, DDG was receiving 31 million direct queries per day.