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:** Several contributors can edit pages, sometimes at the same time.
- **Edit history:** Each change is logged with a time and the editor’s name or IP.
- **Interlinking:** Creating links among pages is straightforward, which helps interconnect content.
- **Lightweight markup:** Formatting is usually handled by lightweight markup languages (e.g., WikiText or Markdown).
- **Permission settings:** Some wikis are open to anyone; others limit edits to registered users or specific groups.
- **Discussion pages:** Dedicated discussion pages enable contributors to coordinate and discuss content.

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

Pros
- **Fast collaboration:** Contributors can rapidly create and improve content.
- **Openness:** Edit histories and talk pages reveal how content decisions were made.
- **Expandable:** Wikis expand easily as contributors add and organize content.

Cons
- **Vandalism and false information:** Open contribution can result in deliberate or accidental misinformation.
- **Inconsistent quality:** Articles can differ greatly in depth, tone, and reliability.
- **Organizational issues:** Poor coordination or governance can cause content fragmentation and disputes.

Notable example
- **Wikipedia** — the largest example, maintained by the Wikimedia Foundation and contributed to by volunteers worldwide.