Anyone with Internet access can write and make changes to Wikipedia articles, except in limited cases where editing is restricted to prevent further disruption or vandalism.

Since its creation on January 15, 2001, Wikipedia has grown into the world's largest reference website, attracting 1.7 billion unique visitors monthly as of November 2020. It currently has more than 55 million articles in more than 300 languages, including 6,263,864 articles in English with 144,828 active contributors in the past month.

The fundamental principles by which Wikipedia operates are the five pillars. The Wikipedia community has developed many policies and guidelines to improve the encyclopedia; however, it is not a formal requirement to be familiar with them before contributing.

Anyone is allowed to add or edit words, references, images, and other media here. What is contributed is more important than who contributes it. To remain, the content must be free of copyright restrictions and contentious material about living people. It must fit within Wikipedia's policies, including being verifiable against a published reliable source. Editors' opinions and beliefs and unreviewed research will not remain. Contributions cannot damage Wikipedia because the software allows easy reversal of mistakes, and many experienced editors are watching to ensure that edits are improvements. Begin by simply clicking the Edit button at the top of any editable page!

Wikipedia is a live collaboration differing from paper-based reference sources in important ways. It is continually created and updated, with articles on new events appearing within minutes, rather than months or years. Because everybody can help improve it, Wikipedia has become more comprehensive than any other encyclopedia. Besides quantity, its contributors work on improving quality, removing or repairing misinformation, and other errors. Over time, articles tend to become more comprehensive and balanced. However, because anyone can click "edit" at any time and add content, any article may contain undetected misinformation, errors, or vandalism. Readers who are aware of this can obtain valid information, avoid recently added misinformation (see Wikipedia:Researching with Wikipedia), and fix the article.