Duplicate Content

Duplicate content exists when identical or very similar content is accessible under multiple URLs. Google must decide which version to index - this can lead to ranking problems. Types: Internal duplicates (e.g., www vs. non-www, HTTP vs. HTTPS, URL parameters), external duplicates (content on multiple domains). Solutions: Set canonical tags, implement 301 redirects, configure URL parameters in Search Console, robots.txt for non-canonical versions, standardize HTTPS and www version. Duplicate content is not a direct penalty but dilutes link equity and can lead to crawl waste.