What is a canonical URL?

A canonical URL is the preferred version of a page that you want search engines to index, specified with a rel=canonical link tag in the page head.

Why do duplicate pages hurt SEO?

Duplicate pages split ranking signals across multiple URLs, diluting the authority of each version and confusing search engines about which one to show.

Where do I add the canonical tag?

Add a link tag with rel=canonical in the head section of each page, pointing to the preferred URL for that content.

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How to Fix Canonical URL Issues on Your Website

SEO Feb 2, 2026 3 min read

What the canonical URL check tests

SiteCurl checks whether each page includes a <link rel="canonical"> tag pointing to the preferred URL. This tag tells search engines which version of a page is the “real” one when the same content is accessible at multiple URLs.

This happens more often than most people realize. Parameters like ?utm_source=newsletter, trailing slashes, HTTP vs HTTPS, and www vs non-www all create different URLs that serve the same content.

Why it matters

Without a canonical tag, search engines may index multiple versions of the same page. This splits link equity and ranking signals across duplicates, weakening the page’s position in results. In some cases, the wrong version gets indexed: Google shows the HTTP version instead of HTTPS, or the parameterized URL instead of the clean one.

A canonical tag consolidates all signals to a single URL. It is one of the simplest and highest-impact technical SEO fixes.

How to fix it

Adding a canonical tag

Add this tag inside the <head> section of every page:

<link rel="canonical" href="https://yoursite.com/page-name">

The href should be the full, absolute URL of the preferred version: HTTPS, with or without www (pick one and be consistent), without tracking parameters.

Self-referencing canonicals

Every page should have a canonical tag that points to itself. This is called a self-referencing canonical. It explicitly tells search engines “this is the right URL” even when no duplicate exists yet.

Common mistakes

Relative URLs: Use absolute URLs (https://yoursite.com/page), not relative (/page). Some search engines handle relative canonicals, but absolute is more reliable.
Pointing to the wrong page: A canonical tag on Page A that points to Page B tells search engines to ignore Page A entirely. Only do this intentionally.
HTTP in canonical on HTTPS page: If your site uses HTTPS, the canonical URL must also be HTTPS. A mismatch sends conflicting signals.

CMS fixes

WordPress: Yoast SEO and Rank Math add canonical tags automatically. Check the advanced settings per page to override. Shopify: Canonical tags are automatic for product and collection pages. For custom pages, edit the <head> in the theme template.

How to verify the fix

View page source and search for rel="canonical". Confirm the URL matches the page’s preferred address. Run a SiteCurl scan to check canonical tags across all your pages at once.

Canonical issues often appear alongside robots.txt problems and redirect chains. Fix them together for cleaner crawlability.

Start a free trial and scan your site to find every canonical tag issue.