Duplicate Content
The same or very similar content appearing at multiple URLs, causing ranking signal dilution.
Duplicate content is substantially the same text reachable at more than one URL, on your site or across sites. There is no penalty for it, but there is a cost: search engines pick one version to show and the others' signals are wasted. Canonical tags, consistent internal linking and redirects resolve it.
Definition
Duplicate content refers to blocks of content that are identical or substantially similar appearing at multiple URLs — either within a single site (internal duplicates) or across different sites (external duplicates). Google does not penalize duplicate content per se, but it can cause ranking dilution.
Why It Matters
When Google finds duplicate content, it must choose which version to show in search results. If it picks the wrong one (or splits signals across duplicates), your intended page may rank poorly or not at all.
Example
An e-commerce site showing the same product at /shoes/red-nike and /sale/red-nike. Fix: add a canonical tag on the sale page pointing to the main product URL.
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