Duplicate content is substantial text that appears at more than one URL, either on your own site or across different sites. It is one of the most misunderstood topics in technical SEO: most duplication is accidental, technical and harmless in itself, but it can still waste crawl time and split ranking signals.
Is there a duplicate content penalty?
No, not in the sense most people fear. Google filters duplicates by choosing one version to show and hiding the rest. A penalty only applies when duplication is deceptive, such as scraping other sites or mass-producing near-identical doorway pages to manipulate rankings.
Common causes on your own site
- HTTP and HTTPS versions both live.
- www and non-www versions both live.
- Trailing slash and non-trailing slash URLs.
- URL parameters for tracking, sorting and filtering.
- Products listed in several categories with different paths.
- Printer-friendly pages and AMP versions.
- Tag and category archives repeating post excerpts.
- Location pages that only swap the town name.
Duplication across sites
Manufacturer product descriptions used by hundreds of retailers, syndicated press releases and scraped articles all create cross-site duplicates. Google tries to show the original or most useful version. If you sell the same products as everyone else, write your own descriptions; it is one of the quickest wins in ecommerce SEO.
How to fix duplicate content
- Pick one preferred domain and 301 redirect the others (HTTPS, www or non-www).
- Add canonicals. A self-referencing canonical tag on every page handles most parameter issues.
- Redirect true duplicates. If two pages cover the same thing, merge them and use a 301 redirect.
- Noindex thin archives that add no value.
- Link consistently to the preferred URL in menus, internal links and sitemaps.
- Rewrite boilerplate so each page has a unique purpose.
Duplicate content vs keyword cannibalisation
Duplication is the same content at different URLs. Keyword cannibalisation is different content on several pages competing for the same query. The fixes overlap: often you merge pages and redirect.
How to find duplicates
- Search Console’s Pages report: “Duplicate without user-selected canonical” and “Alternate page with proper canonical tag”.
- Crawlers like Screaming Frog flag exact and near-duplicate pages.
- Siteliner checks internal duplication; Copyscape finds copies of your text elsewhere.
- Search Google for a distinctive sentence from your page in quotes.
Frequently asked questions
How much duplication is acceptable?
Repeated headers, footers and short legal text are normal. Focus on the main body content.
Someone copied my content. What should I do?
Ask them to remove it or add a canonical. If they refuse, file a DMCA request with Google.
Related terms
See noindex tag, content decay and the SEO encyclopedia.
Mr. SEO
Mr. SEO is the webmaster at SEO TT - SEO tips and tricks, a publication about all things SEO related.