A wiki is a website designed for collaborative editing, letting many people create, update, and organize content directly in a web 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:** 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:** 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:** Separate talk pages allow contributors to discuss edits and structure.

Frequent uses
- Community knowledge bases such as Wikipedia
- Project documentation and internal company knowledge repositories
- Group writing and collaborative note-taking
- Educational and classroom projects

Advantages
- **Fast collaboration:** Multiple people can add and refine content quickly.
- **Openness:** Transparency through revision histories and discussions.
- **Expandable:** They scale organically as users add more pages and topics.

Drawbacks
- **Vandalism and false information:** Open editing may allow intentional or accidental inaccuracies.
- **Inconsistent quality:** Articles can differ greatly in depth, tone, and reliability.
- **Organizational issues:** Lack of structure or rules can lead to disorganization and conflicts.

Example
- **Wikipedia** — the best-known wiki, run by the Wikimedia Foundation and built by volunteer contributors worldwide.