A canonical tag is a single line of HTML that tells Google: "This is the version of this page I want indexed." It solves duplicate content, consolidates PageRank, and prevents your pages from competing against each other in search results. Done wrong, it can silently suppress your most important pages.

What a Canonical Tag Looks Like

<!-- In the <head> of your page -->
<link rel="canonical" href="https://www.example.com/your-page/" />

<!-- For a product page with URL parameters -->
<!-- On https://example.com/product?color=red&size=M -->
<link rel="canonical" href="https://example.com/product" />

When to Use Canonical Tags

URL parameters create duplicates

/products?sort=price and /products?sort=name showing the same content

HTTP and HTTPS versions of a page both exist

http://example.com/page and https://example.com/page are separate URLs

www and non-www versions both exist

www.example.com and example.com serve the same content

Printer-friendly or amp versions exist

/page and /page/amp/ or /page?print=1

Syndicated content published on another site

Guest post on partner site should canonical back to your original article

Canonical Tag Do's & Don'ts

Do This

Use a self-referencing canonical on every page, even if it has no duplicates

Set canonicals to the HTTPS version of the URL

Set canonicals to the www (or non-www) version consistently across your entire site

Include the canonical URL in XML sitemaps — only the canonical version

Use absolute URLs (https://example.com/page), not relative paths (/page)

Don't Do This

Don't point a canonical to a redirected URL — always canonical to the final destination

Don't canonical a noindex page — this creates conflicting signals Google ignores

Don't use canonical to fix near-duplicate content with major differences — use a redirect instead

Don't set different canonicals per device (mobile/desktop) — use a single responsive URL

Don't canonical across domains unless you specifically want to credit another site

Canonical vs. 301 Redirect: When to Use Each

A canonical tag is a hint to Google — it can be ignored if Google detects that the canonical URL is very different from the current page. A 301 redirect is a command — the old URL is permanently replaced. Use a canonical when both versions of a page should remain accessible (e.g., URL parameters). Use a 301 when the old URL should never be accessed directly again.

Common trap: A canonical tag does not remove the non-canonical URL from Google's index immediately. It signals preference. A 301 redirect will eventually cause Google to drop the old URL entirely from its index.

Audit All Canonical Tags on Your Site

SiteGrip crawls your full site and flags canonical conflicts, missing self-referencing canonicals, and canonicals pointing to redirected URLs.

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Canonical Tags: SEO Best Practices & Common Mistakes (2026)