Missing canonical tag: Crawl Audit check 37

Short answer: check 37 fails when the page has no canonical tag at all. Without one, Google picks the main version of a page on its own when it finds duplicates, and it may not pick the one you'd want. The fix is one line in the page's <head>.

What Crawl Audit checks

• Pass: a <link rel="canonical"> tag is present.
• Fail: it isn't.

Check 36 looks at where the canonical points. This one only asks whether it exists, so a missing tag fails both.

What happens without one

Google still chooses a canonical for duplicate pages. It just does it without your input. Search Console labels the result "Duplicate without user-selected canonical": "This page is a duplicate of another page, although it doesn't indicate a preferred canonical page. Google has chosen the other page as the canonical for this page, and so will not serve this page in Search."

We saw that exact status on our own site in September, for https://www.devmarde.com/. The fix there was a permanent redirect from www to the main domain. A canonical tag on the main URL then confirms which one we mean.

How to add one

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

• In the <head>: Google only accepts it there.
• With an absolute URL: Google recommends "absolute paths rather than relative paths".
• For PDFs and other non-HTML files, Google also accepts "a link HTTP response header with a rel="canonical" target attribute", for web search results.

What not to use instead

Google is explicit: "Don't use the robots.txt file for canonicalization purposes." And it doesn't recommend noindex for choosing a canonical either, "because it will completely block the page from Search."

On your platform

• WordPress, Shopify, Wix and Squarespace: most themes and SEO plugins output a canonical tag (Wix documents its default as <link rel="canonical" href="{your-page-url}"/>). If check 37 fails, look for a theme edit or a custom page template that left it out.
• Next.js: pages only get a canonical if you set alternates.canonical in their metadata. Set it in every page or in a shared helper.

Sources

• Google Search Central, How to specify a canonical URL (updated 10 July 2026), checked 3 October 2026.
• Google Search Console Help, Page indexing report.
• Next.js, generateMetadata.