Duplicate Content usually arises when an identical or very similar content under several different URLs appears. This applies both within a domain and at different websites.
Duplicate content can occur in the following cases:
- Content is syndicated, sold, or copied illegally.
- The content of a website is, among other domains or accidentally subdomains (eg without "www") is displayed.
- Contents are duplicated in various categories (such as additionally in a news area).
- The content management system can assign a unique URL to the content.
- In various online shops give the same product attribute filter lists.
One speaks of "Near duplicate content" with very similar content, which can also cause problems. Often copied text blocks (approximately teaser or recurring texts on each side) can be treated by search engines as duplicate content.
