A wiki is a website designed for collaborative editing, letting many people create, update, and organize content directly in a web browser.

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.

Common features
- **Collaborative editing:** Several contributors can edit pages, sometimes at the same time.
- **Edit history:** All edits are stored with timestamps and the author’s name or IP.
- **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:** Separate talk pages allow contributors to discuss edits and structure.

Common 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:** Contributors can rapidly create and improve content.
- **Openness:** Edit histories and talk pages reveal how content decisions were made.
- **Expandable:** Wikis expand easily as contributors add and organize content.

Drawbacks
- **Vandalism and false information:** Open contribution can result in deliberate or accidental misinformation.
- **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 largest example, maintained by the Wikimedia Foundation and contributed to by volunteers worldwide.