Duplicate content
The same or nearly the same page at multiple URLs, leaving search engines to choose which version represents the content.
See it
What it is
Duplicate content is the same or substantially similar material living at more than one URL. Search engines group those URLs and choose a canonical version to index. The copies can come from tracking parameters, print views, HTTP and HTTPS variants, the manufacturer's spec paragraph that every retailer pastes in, or category filters that change the URL without changing the page.
Reach for the diagnosis when the wrong URL appears in search, backlinks point at several versions, or many near-identical pages compete for the same query. Consolidate true copies with a 301 redirect when only one URL is needed, or a rel="canonical" link when alternate URLs must stay available.
Ordinary duplication is usually a canonicalization problem, not a penalty. A canonical is also a hint, not a command: conflicting sitemaps, internal links, redirects, or meaningfully different content can make a search engine choose another URL. Do not canonicalize pages that merely share a template but answer different questions.
Ask AI for it
Audit this site for duplicate content and consolidate each cluster. Normalize HTTP versus HTTPS, www versus non-www, trailing slashes, case, and tracking parameters; use a 301 redirect where only one URL should exist. Where alternates must remain reachable, give the preferred URL a self-referencing rel="canonical" and point each alternate canonical at that preferred URL. Update internal links and the XML sitemap to use only preferred URLs, then verify the selected canonical in Google Search Console URL Inspection. Do not merge pages that answer distinct search intents.