A wiki is a web platform that enables multiple users to collaboratively create, edit, and arrange content through a browser.

Wikis prioritize ease of use and openness: pages can be added or changed without technical expertise, and most track every edit so changes can be reviewed or undone.

Common features
- **Collaborative editing:** Numerous contributors can work on pages, sometimes simultaneously.
- **Edit history:** All edits are stored with timestamps and the author’s name or IP.
- **Interlinking:** It’s easy to create links between pages, forming an interconnected knowledge base.
- **Lightweight markup:** Pages are typically formatted with lightweight markup like WikiText or Markdown.
- **Permission settings:** Some wikis are open to anyone; others limit edits to registered users or specific groups.
- **Discussion pages:** Separate talk pages allow contributors to discuss edits and structure.

Frequent uses
- Community knowledge bases such as Wikipedia
- Project docs and corporate knowledge repositories
- Group writing and collaborative note-taking
- Classroom and educational projects

Advantages
- **Fast collaboration:** Many people can collaborate and iterate quickly on content.
- **Openness:** Visibility into edits and discussions shows how decisions were reached.
- **Expandable:** They scale organically as users add more pages and topics.

Drawbacks
- **Vandalism and false information:** Open editing may allow intentional or accidental inaccuracies.
- **Inconsistent quality:** Content quality may vary widely between pages.
- **Organizational issues:** Without clear governance, content may become fragmented or disputed.

Notable example
- **Wikipedia** — the best-known wiki, run by the Wikimedia Foundation and built by volunteer contributors worldwide.