When to use canonical tags (and when not to)

Canonicals look simple on the surface: a one-line tag that says "the URL that matters is X." The complication is that they are a hint, not a directive - Google reads your canonical, considers it alongside other signals (inbound links, sitemap entries, Hreflang siblings, redirect chains), and picks the URL it thinks is canonical. About 15-20% of the time, that pick disagrees with what you declared. That is the gap most "canonical tag tutorial" articles never explain.

This guide skips the basic "what is a canonical" framing (the tool below covers that) and goes straight to the decision-tree playbook: when to set a canonical, when to leave it alone, what to do when Google picks a different canonical than yours, and how to handle cross-domain syndication.

Check the canonical on any URL right now

Paste any URL below. The tool extracts the live <link rel="canonical">, shows whether it is self-referencing or pointing elsewhere, and flags the common mistakes - relative URLs, mismatched protocol, canonical-to-redirected-URL chains.

The mental model: canonicals consolidate, they do not deindex

The most common misunderstanding about canonicals is treating them as a deindex tool. They aren't. A canonical tag tells Google: "if you find duplicate or near-duplicate content at multiple URLs, treat THIS one as the master and consolidate all ranking signals to it." Google still crawls the non-canonical URLs and may even index them; it just credits the ranking signals to the URL you specified.

The right tools for the right job:

• Canonical tag - "These N URLs are the same thing, treat URL X as the master." Use for tracking parameters, paginated pages, faceted nav, A/B variants, syndicated content.
• 301 redirect - "URL A is gone, the new URL is B." Use for permanent URL moves, slug changes, migrations.
• noindex meta tag - "This URL exists but should never be in search results." Use for thank-you pages, search results pages, internal previews.
• robots.txt Disallow - "Don't crawl this." Use for low-value pages where you want to save crawl budget. Does not deindex.

The decision rule: if the URL should not exist long-term, redirect it (don't canonical it). If the URL should exist but should never be in search, noindex it (don't canonical it). Canonical is for URLs that legitimately exist AND should not compete with the canonical version for rankings.

The self-referencing canonical (and why every indexable page needs one)

Every indexable page should have a canonical tag pointing at itself. This sounds redundant - why declare yourself as your own canonical? Two reasons:

1. Tracking parameter URLs. Without a self-canonical, every variant of /products/widget?utm_source=email is a unique URL Google might index. With a self-canonical pointing at /products/widget, all the parameterized variants consolidate ranking signals onto the clean URL.
2. Scraped / syndicated content. If another site copies your page (with or without permission), having a self-canonical declares yours as the master. The scraper's copy will fall behind in search rankings.

The audit move: every URL on your site should have either a self-referencing canonical (the page itself is canonical) OR a canonical pointing at the master URL (the page is a duplicate / variant of another). A page with NO canonical tag at all is a missed opportunity - Google will pick a canonical for you, and its pick is sometimes wrong.

"Google chose different canonical than user" - what it means and how to fix it

The single most-misunderstood Search Console message. It appears in URL Inspection when Google has decided your canonical declaration is wrong, and it picked a different URL as the canonical. The implications:

• Your declared canonical URL is treated as a non-canonical duplicate. It does not earn rank in its own right.
• The URL Google picked instead is the one earning all the credit. Sometimes that's fine (Google found the real master); sometimes it's wrong (Google picked a parameterized variant or an old URL with stronger backlinks).
• Your sitemap submission is being ignored for the affected URL.

The diagnosis tree:

1. Open URL Inspection in Search Console for the affected URL.
2. Compare "User-declared canonical" with "Google-selected canonical." The difference between the two is the diagnosis.
3. If Google picked a parameterized variant (e.g., your declared canonical is /products/widget but Google picked /products/widget?ref=email), check inbound link patterns - probably more inbound links point at the parameterized URL than at the clean one. Fix by adding canonical tags to the parameterized URLs and reducing inbound-link variation.
4. If Google picked a redirected URL (your canonical points at the new URL but Google still credits the old one), check whether the 301 redirect is actually firing on the old URL - sometimes a CMS upgrade silently breaks the redirect.
5. If Google picked a different page entirely (e.g., your canonical for /blog/post says self-canonical but Google picked /blog/post-revised), the two pages probably have very similar body content. Either consolidate them or differentiate the body.

The fix usually requires aligning multiple signals with your canonical declaration: inbound link anchor text, sitemap entries, internal links, redirects. A canonical tag alone, fighting against contradictory signals from the rest of the site, will lose.

The biggest mistake: a single bad template canonical, repeated 5,000 times

The single most damaging canonical bug on a templated site is a default canonical that points everywhere wrong. Common patterns:

• Every page canonicals to the homepage. Some misconfigured WordPress themes or hand-rolled templates emit <link rel="canonical" href="https://yourdomain.com/"> on every page in the site. Result: Google treats the entire site as one URL, and only the homepage ranks. Catastrophic.
• Every product page canonicals to the category page. A theme template misuses get_canonical() and pulls the parent's URL instead of the page's own. Result: 1,000 product pages all consolidate ranking signals onto the category page, and individual products never rank.
• Mobile-version canonicals point at desktop, but desktop canonicals don't reciprocate. A separate mobile site at m.yourdomain.com sets canonicals back to www.yourdomain.com. Without the desktop pages declaring <link rel="alternate" media="..."> back to mobile, you have a one-way consolidation that can confuse signals.
• HTTPS migration left HTTP canonicals. The site moved to HTTPS years ago, but the template canonical is still hardcoded to http://. Every page now canonicals to a URL that 301s to itself. Sometimes Google figures it out, sometimes it picks the http variant as canonical and indexes that.

The audit move: run 10 pages from different content types through the canonical checker. The canonical should be the page's own URL on its current domain and protocol. Any deviation across the sample is a template bug, and a template bug usually affects every page in the content type. Fix it once, fix it for thousands.

What a clean canonical audit looks like

Run this on a fresh site, after any template change, after any migration, and quarterly on production sites.

1. Sample 10-15 pages across different content types (homepage, blog post, product page, category page, paginated archive, search results, parameterized URL). Run each through the canonical checker.
2. Verify every indexable page has a self-referencing canonical. A page with no canonical at all is a gap. A page canonicalising to a different URL is either intentional (parameterized, paginated) or a template bug (deserves investigation).
3. Spot-check parameterized URLs. Append ?utm_source=test to a URL and re-check. The canonical should still point at the clean URL, not at the parameterized variant.
4. Run URL Inspection on 5 top-traffic pages in Search Console. Compare "User-declared canonical" vs "Google-selected canonical." Mismatches are the priority diagnosis list.
5. Check protocol and trailing-slash consistency. Canonical URLs must match the protocol (HTTPS) and trailing-slash convention (/page/ vs /page) of your live URLs. Inconsistencies here create silent canonical loops.
6. Audit cross-domain syndication. If you syndicate posts to Medium, LinkedIn, or partner sites, every syndicated copy should have a canonical back to your URL. Without it, the partner's copy can outrank yours.

Quick quiz: are you ready to audit your own canonicals?

Five questions, takes two minutes. We'll show you the right answer and a one-line explanation after each one.

Next up in On-Page SEO

Canonicals decide which URL gets ranked when content overlaps. Open Graph tags decide what your page looks like when it gets shared off-Google. From here:

• Open Graph and social previews - the off-Google CTR work most teams ignore.