Stack Overflow is a question and answer site for professional and enthusiast programmers. It is a privately held website, the flagship site of the Stack Exchange Network, created in 2008 by Jeff Atwood and Joel Spolsky. It features questions and answers on a wide range of topics in computer programming. It was created to be a more open alternative to earlier question and answer sites such as Experts-Exchange. The name for the website was chosen by voting in April 2008 by readers of Coding Horror, Atwood's popular programming blog.
The website serves as a platform for users to ask and answer questions, and, through membership and active participation, to vote questions and answers up or down and edit questions and answers in a fashion similar to a wiki or Reddit. Users of Stack Overflow can earn reputation points and "badges"; for example, a person is awarded 10 reputation points for receiving an "up" vote on a question or an answer to a question, and can receive badges for their valued contributions, which represents a gamification of the traditional Q&A site. Users unlock new privileges with an increase in reputation like the ability to vote, comment, and even edit other people's posts. All user-generated content is licensed under Creative Commons Attribute-ShareAlike license, version 2.5, 3.0, or 4.0 depending on the date the content was contributed.
Closing questions is a main differentiation from other Q&A sites like Yahoo! Answers and a way to prevent low quality questions. The mechanism was overhauled in 2013; questions edited after being put "on hold" now appear in a review queue. Jeff Atwood stated in 2010 that duplicate questions are not seen as a problem but rather they constitute an advantage if such additional questions drive extra traffic to the site by multiplying relevant keyword hits in search engines.
Stack Overflow also has a Jobs section to assist developers in finding their next opportunity. For employers, Stack Overflow provides tools to brand their business, advertise their openings on the site, and source candidates from Stack Overflow's database of developers who are open to being contacted.