SEO basics

How to fix: Canonical tag

A canonical tag tells search engines which URL is the preferred version of a page when the same content is reachable at several addresses.

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Why it matters

The same page often exists at example.com/page, www.example.com/page, with a trailing slash, or with tracking parameters. Without a canonical hint, search engines have to guess which one to show, which can split signals between versions.

How to check

Look for <link rel="canonical" href="..."> in <head>. The URL should be absolute and normally point to the page itself.

How to fix it

HTML

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

Next.js

export const metadata = {
  alternates: { canonical: '/page' },
};

Common mistakes

Pointing every page's canonical at the homepage.
Using a relative URL or one that redirects.
Mixing www and non-www: pick one, redirect the other to it, and use it in every canonical.

Frequently asked questions

Is canonical a command?

It's a strong hint, not a guarantee; search engines can choose a different URL.

Related guides

Guidance is general. Test header and DNS changes on a staging copy first, and check your hosting provider's documentation for platform-specific steps.