A wiki is a web platform that enables multiple users to collaboratively create, edit, and arrange content through a 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.

Common features
- **Collaborative editing:** Numerous contributors can work on pages, sometimes simultaneously.
- **Edit history:** Every modification is recorded with a timestamp and the editor’s identity or IP address.
- **Interlinking:** Creating links among pages is straightforward, which helps interconnect content.
- **Lightweight markup:** Simple markup languages (such as WikiText or Markdown) are used to format pages.
- **Permission settings:** Access controls vary — from fully open editing to permissions for certain users or groups.
- **Discussion pages:** Dedicated discussion pages enable contributors to coordinate and discuss content.

Common uses
- Community-driven knowledge bases (for example, Wikipedia)
- Project docs and corporate knowledge repositories
- Collaborative writing and shared note-taking
- School and instructional projects

Pros
- **Fast collaboration:** Contributors can rapidly create and improve content.
- **Openness:** Visibility into edits and discussions shows how decisions were reached.
- **Expandable:** They scale organically as users add more pages and topics.

Cons
- **Vandalism and false information:** Public editing can lead to vandalism or incorrect information.
- **Inconsistent quality:** Content quality may vary widely between pages.
- **Organizational issues:** Without clear governance, content may become fragmented or disputed.

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