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Use canonical tags and fix duplicate content

Tell search engines which URL is the preferred version of a page, and consolidate pages that repeat the same content.

Intermediate 30 minutes By WebGrowthEngine team · Updated Oct 14, 2026

The problem

Pages have no canonical tag, canonical tags point at broken or redirecting URLs, or several URLs show identical or nearly identical content.

How to spot it

  • The same content is reachable at several addresses (with and without parameters, trailing slashes, uppercase letters, or print versions).
  • The audit lists exact or near-duplicate groups and canonical tags whose target returns an error.

Why it matters

When the same content lives at several URLs, ranking signals are split between them and search engines must guess which one to show. A canonical tag states your preference.

What happens if you leave it

The wrong URL may appear in search, pages may compete with each other, and a canonical pointing at a broken URL can keep a good page out of the index.

How to fix it

  1. Add a self-referencing canonical to every indexable page, using the absolute final URL:

    <link rel="canonical" href="https://www.example.com/services/plumbing/">

  2. On duplicate variants (tracking parameters, sort orders, print pages), point the canonical at the main version.

  3. Fix canonicals that point at errors or redirects: change them to the final URL that returns 200.

  4. For exact duplicates that serve no purpose, 301-redirect the copies to the main page.

  5. For near-duplicates such as location or product pages that differ only by a word, either make each one genuinely useful (unique details, photos, FAQs) or merge them into one stronger page.

Platform-specific notes

  • WordPress: SEO plugins output canonical tags automatically; check that they use your preferred host and protocol.
  • E-commerce filters: canonicalise filtered and sorted listing URLs to the main category page unless the filtered page targets a distinct search.

Common mistakes

  • Canonicalising every page to the homepage.
  • Pointing a canonical at a page that is noindex or blocked by robots.txt.
  • Relative or protocol-less canonical URLs.

How to check the fix worked

View the page source and search for rel="canonical"; open that URL and confirm it loads with HTTP 200 without redirecting. Re-run the audit; the duplicate groups should shrink.

References and further reading

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