||It has been suggested that Stack Overflow sister sites be merged into this article. (Discuss) Proposed since April 2013.|
|Type of site||Question & Answer|
|Owner||Stack Exchange Inc.|
|Created by||Jeff Atwood and Joel Spolsky|
|Launched||September 2009 (relaunched in January 2011)|
The Stack Exchange Network (also called StackExchange) is a group of question-and-answer Web sites on topics in many different 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 is designed to allow the sites to be self-moderating.
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. 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.
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 Careers 2.0 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.
Censorship attempt by CipherCloud
On 18 April 2013 CipherCloud issued DMCA takedown notices in an attempt to block discussion of possible weaknesses of their encryption algorithm. The StackExchange Crypto group discussion on the algorithm  was censored, but was later restored without pictures. Image analysis indicates that these pictures, which are screenshots of CipherCloud in operation encrypting a GMail message, may have been faked by CipherCloud.
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