Wikis are websites built for collaborative authoring, allowing numerous contributors to add, edit, and structure content online.

They emphasize simplicity and openness — pages can be created or modified without special technical skills, and most maintain an edit history so revisions can be reviewed or reverted.

Key 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:** It’s easy to create links between pages, forming an interconnected knowledge base.
- **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:** Talk or discussion pages let contributors debate edits and organization.

Common uses
- Community-driven knowledge bases (for example, Wikipedia)
- Project documentation and internal company knowledge repositories
- Cooperative writing and shared notes
- School and instructional projects

Pros
- **Fast collaboration:** Many people can collaborate and iterate quickly on content.
- **Openness:** Edit histories and talk pages reveal how content decisions were made.
- **Expandable:** Wikis can grow naturally as contributors add new topics.

Drawbacks
- **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:** 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.