Canonical URLs and duplicate content

The same content is often reachable at several URLs — with and without a trailing slash, with tracking parameters, on www and the bare domain, over http and https. Search engines need to know which URL is the real one so ranking signals aren't split across duplicates. That's what a canonical link does.

<link rel="canonical" href="https://example.com/pricing">

The golden rule: point to the 200

A canonical must point to the URL that actually returns the page (HTTP 200) — not a URL that redirects, and not a different page. If /pricing canonicalises to a URL that 301-redirects back to /pricing, you've created a confusing loop; if it points to your homepage, you've told Google the pricing page is a duplicate of the homepage and it may drop from results.

Self-referencing is good

Most pages should declare themselves as canonical. A self-referencing canonical is not redundant — it disambiguates parameterised and slash variants of the same page.

Keep it consistent with everything else

• The canonical, the sitemap entry, and internal links should all use the same URL form (same host, same scheme, same trailing-slash convention).
• Don't canonicalise across genuinely different content.
• Cross-domain canonicals are valid but only when the content really is the same.
• Redirects and canonicals should agree, never fight each other.

How to fix it

1. For each page, confirm the canonical points to a URL that returns 200 with the same content.
2. Make the canonical, sitemap and internal links use one consistent URL form.
3. Remove canonicals that point at redirects or the homepage by mistake.
4. Re-scan and check coverage in Google Search Console.