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:** Multiple people can edit the same pages, occasionally concurrently.
- **Edit history:** All edits are stored with timestamps and the author’s name or IP.
- **Interlinking:** It’s easy to create links between pages, forming an interconnected knowledge base.
- **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:** Dedicated discussion pages enable contributors to coordinate and discuss content.

Typical uses
- Crowd-sourced knowledge resources (e.g., Wikipedia)
- Project documentation and internal company knowledge repositories
- Group writing and collaborative note-taking
- School and instructional projects

Benefits
- **Fast collaboration:** Multiple people can add and refine content quickly.
- **Openness:** Visibility into edits and discussions shows how decisions were reached.
- **Expandable:** Wikis can grow naturally as contributors add new topics.

Cons
- **Vandalism and false information:** Open contribution can result in deliberate or accidental misinformation.
- **Inconsistent quality:** Content quality may vary widely between pages.
- **Organizational issues:** Without clear governance, content may become fragmented or disputed.

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