What does a canonical tag actually do?

It tells search engines which URL is the "master" copy when the same or near-identical content is reachable at more than one URL - the crawled duplicate's ranking signals get consolidated onto the canonical target instead of split across both.

Does Scanverra validate that my canonical tag is correct?

Partly, and it's genuinely useful. The Website Audit's SEO score runs Lighthouse's canonical check, which flags a relative (non-absolute) URL, an invalid URL, multiple conflicting canonical tags on one page, and the common mistake of every page canonicalizing to your homepage instead of itself. Browser Test additionally shows you the raw tag and its exact value. What neither checks: whether the canonical target actually returns a 200 (versus a redirect or 404), and whether it's consistent with your site's chosen protocol/subdomain across every page - those still need a manual spot-check.

Should the canonical URL be absolute or relative?

Absolute, always - a relative canonical path is technically against the spec and can be resolved incorrectly by different crawlers, especially on a site served from multiple subdomains or protocols.

Can a page canonicalize to a URL that returns a redirect or a 404?

It can, but it shouldn't - a canonical pointing at a redirect or broken URL sends a confusing signal and search engines may just ignore it. Since Scanverra doesn't check this for you, verify the canonical target actually returns a 200 and matches the content, especially after a URL restructure.

How to Fix Canonical URL Issues

Why Canonical Tags Go Wrong

URL parameters creating unintended duplicates. Tracking parameters, sort order, or filter state (?utm_source=, ?sort=price) generate technically-different URLs serving the same content, without a canonical pointing them back to the clean version.
Protocol or subdomain mismatches. http vs. https, or www vs. bare domain, splitting the same content across two indexed addresses.
Pagination without a self-referencing or series-aware canonical.Page 2 of a paginated list canonicalizing to page 1 (or not having a canonical at all) can make search engines drop page 2's unique content entirely.
Staging or preview URLs leaking a canonical pointing at production, or vice versa, after a template gets copied between environments.

How to Identify the Problem

The Website Audit's SEO score runs a real canonical-correctness check on every scan - it flags a canonical URL that's relative instead of absolute, one that's outright invalid, multiple conflicting canonical tags on the same page, and the specific, common mistake of a page canonicalizing to your homepage instead of to itself. Browser Test complements this by showing you the raw tag and exact URL it captured from your live, rendered page.

Neither check confirms the canonical target actually resolves to a 200 (rather than a redirect or a 404), or that it's consistent with your site-wide protocol/subdomain choice - those two still need a manual spot-check.

How to Fix It

1. Self-reference the canonical URL on the preferred version of a page

A page canonicalizing to its own clean, absolute URLtypescript

1export const metadata = {
2  alternates: {
3    canonical: "https://example.com/products/keyboard",
4  },
5};

Or directly in HTML:

Always use the absolute URL, never a relative pathhtml

1<link rel="canonical" href="https://example.com/products/keyboard" />

2. Canonicalize parameter and sort/filter variants back to the clean URL

A page reachable as both /products?sort=price and /productsshould have the parameterized version's canonical point at the clean /products URL, so link equity and indexing consolidate onto one address.

3. Pick one protocol and one host, everywhere

Standardize on https and either www or the bare domain, redirect the other permanently (301), and make sure every canonical tag on the site uses that same standard - a canonical pointing at the non-redirected version defeats the purpose.

4. Manually verify the canonical target actually resolves

Run a Website Audit first - it'll catch relative URLs, invalid URLs, conflicting canonicals, and the homepage-mistake automatically. What's left to check by hand: that the canonical URL returns a 200 status and genuinely matches the content of the page pointing to it, especially right after a URL restructure or migration.

How Scanverra Detects This

The Website Audit's SEO score (Lighthouse's canonical audit) parses every rel="canonical"link on the page and flags a relative or invalid URL, multiple conflicting canonicals, and a canonical pointing at your homepage's root instead of the page itself. Browser Test separately captures whether a canonical tag is present and the exact URL it points to. Together they cover the mistakes above - what they can't see is whether the target URL actually resolves correctly or matches the source page's content.