Imagine a world in which every single person on the planet is given free access to the sum of all human knowledge. That's what we're doing.

— Jimmy Wales, co-founder

Wikipedia was founded in 2001 as a project to build an online, free-access, free-content encyclopedia entirely from scratch. Since then, it has grown to be the largest encyclopedia ever created, comprising more than five million articles in English, while still relying on the contributions of volunteers. The English Wikipedia community thanks the millions of users whose edits over the past fourteen-plus years have made this remarkable accomplishment possible.

Wikipedia officially launched on 15 January 2001, with Jimmy Wales and Larry Sanger as its leaders, on a single computer server as the successor to Nupedia. Its first major mainstream media coverage was in The New York Times on 20 September 2001. In the first year of its existence, more than 20,000 encyclopedia entries were created – a rate exceeding 1,500 articles per month. Today, there are Wikipedia editions in more than 200 languages, accompanied by a dozen additional free-content projects, such as Wikimedia Commons. In March 2006, the English Wikipedia reached one million articles. According to Alexa, Wikipedia is currently the world's sixth most popular website, receiving approximately eight billion pageviews per month. We reached five million articles on 1 November 2015.

While Wikipedia is an incredible success, it remains a work in progress. There are still great gaps in its coverage with millions of important topics missing from its pages. Many articles – even vital ones – are not yet considered high-quality. Of our five million articles, only a few tens of thousands have passed a vetting process for good or featured status, and more than half are short stubs or start-class articles. There are also more than 200 non-English-language editions of Wikipedia that need volunteers. In other words, there is still much work to be done – and you can help!

Wikipedia is written by the people who use it. Anyone, regardless of background, can contribute to building the encyclopedia. You don't even have to register an account (though there are good reasons to do so). If you find an article you can improve, edit the article to make it more accurate and useful for others. Each page contains edit buttons for you to make those changes immediately. Any improvement, whether it's fixing a typo or drafting a brand new article, is greatly appreciated.

Wikipedia values boldness and the pursuit of consensus. Don't be afraid or disillusioned if your first contributions are undone – Wikipedia is a collaborative project, which means that sometimes we disagree. That's okay. Each page on Wikipedia has a talk page dedicated to discussing improvements, and fellow editors have a talk page where you can contact them individually.

If you're new here, firstly: welcome. We sincerely hope you like it here and decide to stay. Below are some helpful links to get you started:

• Five pillars of Wikipedia – the fundamental principles that guide our decision-making
• Research help – Strategies for utilizing Wikipedia's knowledge
• Tutorial – a simple nine-page guide on the basics of Wikipedia editing
• The Wikipedia Adventure – an interactive one-hour tour that will help you engage in the basics of editing
• Contributing to Wikipedia – a one-hour comprehensive outline of the basics of contributing

If you want to find an article to improve, here are some pointers and areas to contribute:

• Wikipedia:Community portal – collaborations, tasks, and news about the English Wikipedia
• Wikipedia:WikiProject Council/Directory – A directory of WikiProjects, which are groups of editors working to improve articles within each project's scope
• Wikipedia:Vital articles – Topics on which the English Wikipedia should have corresponding high-quality articles
• This week's article for improvement is Jetty

If you get stuck, a variety of resources are available to assist you. The page Wikipedia:Questions lists locations where you can ask for help. The most valuable assets, however, are your fellow Wikipedians. If you have any questions about editing Wikipedia, friendly Wikipedians at the Teahouse will be more than happy to provide answers. You can also meet Wikipedians in person in many places around the world; see Wikipedia:Meetup for more information.

If you are already a Wikipedian, thank you for your contributions. We hope you continue to contribute to this amazing compendium of human knowledge.