A wiki is a website designed for collaborative editing, letting many people create, update, and organize content directly in a web 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.

Key features
- **Collaborative editing:** Numerous contributors can work on pages, sometimes simultaneously.
- **Edit history:** Each change is logged with a time and the editor’s name or IP.
- **Interlinking:** Links between pages are simple to create, helping build connected content.
- **Lightweight markup:** Pages are typically formatted with lightweight markup like WikiText or Markdown.
- **Permission settings:** Wikis may allow public editing or restrict changes to registered or authorized users.
- **Discussion pages:** Talk or discussion pages let contributors debate edits and organization.

Common uses
- Community knowledge bases such as Wikipedia
- Project docs and corporate knowledge repositories
- Group writing and collaborative note-taking
- School and instructional projects

Pros
- **Fast collaboration:** Contributors can rapidly create and improve content.
- **Openness:** Edit histories and talk pages reveal how content decisions were made.
- **Expandable:** They scale organically as users add more pages and topics.

Drawbacks
- **Vandalism and false information:** Public editing can lead to vandalism or incorrect information.
- **Inconsistent quality:** Entries may vary in accuracy, style, and completeness.
- **Organizational issues:** Without clear governance, content may become fragmented or disputed.

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