Type of site
|Question & Answer|
|User contributions under CC BY-SA 3.0|
|Owner||Stack Exchange Inc.|
|Created by||Jeff Atwood and Joel Spolsky|
|Launched||September 2009 (relaunched in January 2011)|
|167 (March 2015)[update]|
Stack Exchange is a network of question and answer websites on topics in varied fields, each site covering a specific topic, where questions, answers, and users are subject to a reputation award process. The sites are modeled after Stack Overflow, a forum for computer programming questions that was the original site in this network. The reputation system allows the sites to be self-moderating. User contributions are licensed under Creative Commons Attribution-ShareAlike 3.0 Unported.
In 2008, Jeff Atwood and Joel Spolsky created Stack Overflow, a question-and-answer Web site for computer programming questions, which they described as an alternative to the programmer forum Experts-Exchange. In 2009, they started additional sites based on the Stack Overflow model: Server Fault for questions related to system administration and Super User for questions from computer "power users".
In September 2009, Spolsky's company Fog Creek Software released a beta version of the Stack Exchange 1.0 platform as a way for third parties to create their own communities based on the software behind Stack Overflow, with monthly fees. This white label service was not successful, with few customers and slowly growing communities.
In May 2010, Stack Overflow (as its own new company) raised $6 million in venture capital from Union Square Ventures and other investors, and it switched its focus to developing new sites for answering questions on specific subjects, Stack Exchange 2.0. Users vote on new site topics in a staging area called "Area51", where algorithms determine which suggested site topics have critical mass and should be created. In November 2010, Stack Exchange site topics in "beta testing" included physics, math, and writing. Stack Exchange publicly launched in January 2011 with 33 websites; it had 27 employees and 1.5 million users at the time, and it included advertising. At that time, it was compared to Quora, founded in 2009, which similarly specializes in expert answers. Other competing sites include WikiAnswers and Yahoo! Answers.
In February 2011, Stack Overflow released an associated job board called Careers 2.0, charging fees to recruiters for access, which later re-branded to Stack Overflow Careers. In March 2011, Stack Overflow raised $12 million in additional venture funding, and the company renamed itself to Stack Exchange, Inc. It is based in Manhattan, New York City. In February 2012, Atwood left the company.
On 18 April 2013 CipherCloud issued DMCA takedown notices in an attempt to block discussion of possible weaknesses of their encryption algorithm. The Stack Exchange Crypto group discussion on the algorithm  was censored, but it was later restored without pictures.
The primary purpose of each Stack Exchange site is to enable users to post questions and answer them. Users can vote on both answers and questions, and through this process users earn reputation points, a form of gamification. This voting system was compared to Digg when the Stack Exchange platform was first released. Users receive privileges by collecting reputation points, ranging from the ability to vote and comment on questions and answers to the ability to moderate many aspects of the site. Due to the prominence of Stack Exchange profiles in web search results and the Stack Overflow Careers job board, users may have reason to game the system. Along with posting questions and answers, users can add comments to them and edit text written by others. Each Stack Exchange site has a "meta" section where users can settle disputes, in the style of MetaFilter's "MetaTalk" forum, because the self-moderation system for questions and answers can lead to significant arguments.
All user-generated content (questions and answers) posted on the Stack Exchange Network is copyright by the contributor and licensed to Stack Exchange under the Creative Commons Attribution Share Alike (CC-BY-SA) license. 
Stack Exchange uses IIS and MS SQL servers, and the ASP.NET framework, from a single code base for every Stack Exchange site. (Except Area51, which runs off a fork of the SO code base.) Blogs run under WordPress. The team also notably uses Redis, HAProxy and Elasticsearch.
Stack Exchange tries to stay up to date with the newest technologies from Microsoft usually using the latest releases of any given framework. The code is primarily written in C# ASP.NET-MVC using the Razor View Engine. The preferred IDE is Visual Studio and the data layers uses Dapper for data access.
Site creation process
- Discussion: The Stack Exchange meta site should provide a forum for discussing potential new ideas labeled a future Stack Exchange site.
- Proposal: A public proposal must be drafted and posted so that any member of the community can discuss the proposal and vote on it. This allows a collaborative proposal to emerge over time. The proposal must address these four key issues:
- the topic of the website
- the targeted audience
- forty exemplary questions, upvoted at least 10 times from the community
- sixty followers from the community
- Commitment: 200 users interested in the new site are asked to formally commit and support the site by actively participating and contributing to it.
- Private Beta: If the concept receives 100% commitment, the site enters the private beta phase, where committed members begin actively using the site and publicizing it.
- Public Beta: The site is open to the public for a long period. This allows the creators to ensure that the site reaches critical mass before it is fully launched.
- Graduation: The site is evaluated on multiple criteria such as the number of answered questions, new questions per day, and registered users. If it meets these criteria and is deemed "sustainable", it is granted a “graduation” and fully launched.
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