SiteAud!tLint Support

Opportunity Technical SEO

Missing canonical tag

Severity
Opportunity
Impact
Low
Effort to fix
Low
Issue code
canonical_missing

Why it matters

Without a canonical tag, search engines pick the preferred version of duplicate or parameter URLs on their own.

How to fix it

Add a self-referencing <link rel="canonical" href="..."> in the head.

What this means

The page has no canonical tag. A canonical tag names the preferred URL for a page's content:

<link rel="canonical" href="https://example.com/running-shoes">

Why it matters

Without a canonical, search engines choose the main URL themselves whenever the same page is reachable at more than one address, for example with tracking parameters, a trailing slash, uppercase letters, or through several categories. Usually they choose well. A self-referencing canonical on every page removes the guesswork and consolidates links pointing at the variations.

This is an opportunity, not an error. A site with clean, consistent URLs works without canonicals; they are a safety net.

How to add canonicals

  1. Add a canonical tag to every indexable page template, pointing at the page's own clean URL: the final HTTPS address, the preferred host, and no tracking parameters.
  2. Use absolute URLs, including https:// and the domain.
  3. On copies of a page, such as a product in a second category or a filtered view, point the canonical to the main version instead. See Canonical points to another URL.
  4. Keep canonicals consistent with internal links, redirects and the XML sitemap. All four should name the same URL.

Most CMS platforms and SEO plugins output self-referencing canonicals once enabled.

Common mistakes

  • Every page canonicalised to the home page by a template bug.
  • A canonical that points to a redirecting or non-200 URL.
  • A canonical added by both the theme and a plugin, with different values.

Verify the fix

Recrawl. The URL details show the canonical found for each page.

How it affects your score

Finding this issue on any page costs the Technical SEO score 0.5 points, plus up to 4 more depending on the share of crawled pages affected. A smaller improvement with a modest effect on its own.

Find the affected URLs

Open Crawl > Issues and pick Missing canonical tag. Each affected URL is listed with its evidence, and Copy URLs or Export URLs hands the list to a developer. The issue also appears in the Action Plan, ranked by impact (low) and effort (low), and in the issues CSV under the code canonical_missing. After fixing, run a new audit and use Compare to confirm the URLs moved to fixed.