ONPAGE · SEO GLOSSARY
Duplicate Content
Identical or substantially similar content appearing at multiple URLs — which forces Google to choose one version to index and can dilute ranking signals across copies.
Definition
Duplicate content occurs when the same (or very similar) content is accessible at multiple URLs. Types: (1) exact duplicates — the same page at http:// and https://, with and without www, with a trailing slash and without; (2) near-duplicates — paginated versions of the same listing, URL parameter variations (`/products?sort=price` vs. `/products?sort=name`); (3) syndicated content — the same article published on multiple sites. Google does not penalise duplicate content per se (it's not a "penalty" in the manual action sense), but it must choose which version to index and rank — and may choose the wrong one. Duplicate content also splits link equity between versions.
Why it matters for SEO
The most common duplicate content issue is HTTP vs. HTTPS or www vs. non-www duplication — if both serve the same content, Google must pick a canonical version, and the link equity from external links pointing to either version gets split. The fix is a 301 redirect from all non-canonical versions to the canonical, plus a self-referencing canonical tag on the canonical version. URL parameter duplication (filtering, sorting, pagination) is the second most common — handled with canonical tags or by blocking parameters in robots.txt.
How DeepSEOAnalysis checks this
The audit checks for: duplicate title tags (a strong signal of duplicate content), multiple URLs serving identical or near-identical content (measured by text similarity), canonical tags that disagree with redirect logic, and URL parameter combinations that generate duplicate pages. It also checks whether pagination is handled with rel=next/prev or canonical.
Useful tools and resources
GLOSSARY
Related terms
technical
Canonical URL
The preferred URL for a page, declared via <link rel="canonical"> to prevent duplicate content from splitting ranking signals.
Read definition →onpage
Thin Content
Pages with little or no unique value — low word count, duplicated from other sources, or auto-generated — that Google may ignore or penalize.
Read definition →technical
Robots.txt
A text file at the root of a domain that tells crawlers which pages or sections to access or avoid.
Read definition →technical
Noindex
A directive that tells search engines not to include a page in their index — implemented via a meta tag or HTTP header.
Read definition →technical
301 Redirect
A permanent HTTP redirect that passes ~90–99% of link equity from the old URL to the new one — the correct redirect type for permanent URL changes in SEO.
Read definition →See how your site scores on Duplicate Content.
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