Duplicate content: what it is and how to fix it

What is duplicate content

Duplicate content is when identical or very similar content is available at multiple URLs. It is one of the most common technical SEO problems.

Пример дублирования:
https://example.com/page
https://www.example.com/page
https://example.com/page/
https://example.com/page?source=newsletter

All four URLs contain the same content — these are duplicates.

Why duplicate content is harmful

When Google finds multiple versions of the same page, it:

• Does not know which version to show in search results
• Splits link equity between the duplicates
• Spends crawl budget crawling duplicate pages
• May choose the “wrong” version to show

In rare cases, Google may apply penalties for clear manipulation, but more often SEO performance simply declines.

Common sources of duplicate content

Technical duplicates

• http:// vs https://
• www vs without www
• With a trailing slash vs without one (/page vs /page/)
• URL parameters (?page=1, ?sort=price, ?utm_source=...)
• Session IDs in URLs

Content duplicates

• The same products in multiple categories
• Printable versions of pages
• Regional versions with minimal differences
• Syndicated content (republishing other people’s articles)

Methods for fixing duplicate content

1. Canonical tag

The main method is to specify the “primary” version:

<!-- На всех вариантах страницы указываем на каноническую -->
<link rel="canonical" href="https://example.com/page">

2. 301 redirect

For technical duplicates, redirect to the primary URL:

# www → без www
server {
    server_name www.example.com;
    return 301 https://example.com$request_uri;
}

# http → https
server {
    listen 80;
    return 301 https://$host$request_uri;
}

3. Noindex for duplicates

If canonical is not applicable:

<meta name="robots" content="noindex">

4. URL parameters in Google Search Console

Tell Google how to handle sorting and filtering parameters.

Check for duplicates with reChecker

Use Canonical Checker to check your canonical tag setup. The tool shows:

• Whether a canonical tag is present and correctly configured
• Whether the canonical matches the current URL
• Conflicts between the meta canonical and the HTTP header

FAQ

Is paraphrased content a duplicate? No. Google identifies duplicate content based on a high degree of textual similarity. Uniquely rewritten content is not a duplicate. “Spinning” (automatic paraphrasing) is usually detected.

What about duplication between websites (external duplication)? If your content is republished on another website, use canonical or request its removal. Google usually identifies the original source, but it is better to take precautions.

Should a small website be concerned about duplicate content? Duplicate content is less critical on a small website. But technical duplicates (www/non-www, http/https) should be fixed even on a small site.