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

They emphasize simplicity and openness — pages can be created or modified without special technical skills, and most maintain an edit history so revisions can be reviewed or reverted.

Common features
- **Collaborative editing:** Several contributors can edit pages, sometimes at the same time.
- **Edit history:** Every modification is recorded with a timestamp and the editor’s identity or IP address.
- **Interlinking:** Links between pages are simple to create, helping build connected content.
- **Lightweight markup:** Pages are typically formatted with lightweight markup like WikiText or Markdown.
- **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
- Community knowledge bases such as Wikipedia
- Internal documentation and company knowledge bases
- Cooperative writing and shared notes
- School and instructional 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:** Open contribution can result in deliberate or accidental misinformation.
- **Inconsistent quality:** Content quality may vary widely between pages.
- **Organizational issues:** Poor coordination or governance can cause content fragmentation and disputes.

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