Definition
Duplicate content is substantially the same content appearing at more than one URL, on the same site or across different sites.
Duplicate content explained
Most duplicate content is accidental and technical: HTTP and HTTPS versions, www and non-www, trailing slashes, URL parameters, printer-friendly pages, faceted filters, and products listed in several categories. Other duplication comes from content itself, such as manufacturer descriptions reused by many retailers or location pages that differ only by the city name.
Duplicate content is not usually a penalty issue. The problem is dilution and choice: search engines pick one version to show, which may not be the one you want, and links and signals are split across the copies. Large-scale duplication can also waste crawl budget and make a site look low in value.
Fixes depend on the cause: redirect duplicate hostnames and protocols to one version, set canonical tags on parameter and variant URLs, keep filter combinations out of the index, and write unique content for pages that deserve to rank on their own.
Example
Your site loads at both http and https, with and without www, giving every page four addresses. Redirecting all versions to https with www, and setting matching canonical tags, turns four competing copies of each page into one.
Why it matters
Consolidating duplicates makes it clear which URL should rank and concentrates all its signals there.
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Related terms
- Canonical tagA canonical tag is an HTML link element that tells search engines which URL is the preferred version of a page when similar or duplicate versions exist.
- Keyword cannibalizationKeyword cannibalization is when several of your pages target the same search intent and compete, so none ranks as well as one strong page would.
- 301 redirectA 301 redirect is a permanent redirect: the server tells browsers and search engines that a URL has moved for good and sends them to the new address.
- Faceted navigationFaceted navigation lets shoppers filter a category by attributes such as size, color, brand or price, often creating a separate URL for each combination.