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.

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:** Simple markup languages (such as WikiText or Markdown) are used to format pages.
- **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 documentation and internal company knowledge repositories
- Cooperative writing and shared notes
- Classroom and educational projects

Pros
- **Fast collaboration:** Multiple people can add and refine content quickly.
- **Openness:** Edit histories and talk pages reveal how content decisions were made.
- **Expandable:** They scale organically as users add more pages and topics.

Limitations
- **Vandalism and false information:** Public editing can lead to vandalism or incorrect information.
- **Inconsistent quality:** Articles can differ greatly in depth, tone, and reliability.
- **Organizational issues:** Poor coordination or governance can cause content fragmentation and disputes.

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