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

Simplicity and openness are central to wikis: anyone can often add or change pages without technical knowledge, and edits are usually logged for review or rollback.

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:** 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:** Wikis may allow public editing or restrict changes to registered or authorized users.
- **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
- Cooperative writing and shared notes
- School and instructional projects

Pros
- **Fast collaboration:** Contributors can rapidly create and improve content.
- **Openness:** Transparency through revision histories and discussions.
- **Expandable:** Wikis can grow naturally as contributors add new 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.

Illustration
- **Wikipedia** — a well-known wiki operated by the Wikimedia Foundation and written by volunteers around the globe.