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

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.

Key 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:** Some wikis are open to anyone; others limit edits to registered users or specific groups.
- **Discussion pages:** Dedicated discussion pages enable contributors to coordinate and discuss content.

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

Benefits
- **Fast collaboration:** Many people can collaborate and iterate quickly on content.
- **Openness:** Transparency through revision histories and discussions.
- **Expandable:** Wikis expand easily as contributors add and organize content.

Limitations
- **Vandalism and false information:** Open contribution can result in deliberate or accidental misinformation.
- **Inconsistent quality:** Content quality may vary widely between pages.
- **Organizational issues:** Lack of structure or rules can lead to disorganization and conflicts.

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