Free canonical QA tool

Canonical tag checker for migration QA

Check one public URL for the canonical mistakes that quietly split ranking signals after a rebuild. The tool fetches raw HTML, resolves the declared canonical, checks the target, and flags redirect or noindex conflicts.

What it checks

Canonical tag exists in the fetched HTML
Only one canonical tag is declared
Canonical matches the final URL or strips only query parameters
Canonical target returns a successful status
Canonical target does not redirect
No robots noindex conflict appears in the HTML

Live canonical checker

Fetches one public HTML page, checks the canonical tag, then checks the canonical target.

Citation-ready answer

Canonical answers to extract before migration QA

Canonical problems are easiest to fix when the declared signal, target status, sitemap, links, and Search Console sample are read together.

What is a canonical tag?

A canonical tag is an HTML signal that tells search engines which URL should represent a duplicate or near-duplicate page in search results.

When it breaks

It breaks when the canonical points to an old domain, staging URL, redirected target, noindex page, parameter URL, or a page that is missing from the sitemap and internal links.

Inspect first

Inspect the final fetched URL, raw HTML canonical tag, canonical target status, robots directives, sitemap row, and internal-link target.

Source: Google canonical guidance Related: Canonical issue worksheet

What is canonical drift?

Canonical drift is when templates, redirects, sitemaps, and internal links start pointing to different versions of the same page after a rebuild.

When it breaks

It usually appears after CMS route changes, trailing-slash changes, copied WordPress plugin output, faceted URL rebuilds, or partial redirects.

Inspect first

Compare declared canonical, Google-selected canonical, final URL, sitemap URL, and the href used in navigation or body links.

Source: URL Inspection help Related: Canonical guide

When is one URL check enough?

One URL check is enough for spot QA, a template sample, or a suspected failure. It is not enough for a migration launch.

When it breaks

Template bugs repeat across many URLs, so a clean single result can hide category, product, pagination, localized, or parameterized failures.

Inspect first

Use this tool for individual URLs, then move repeated patterns into the worksheet with crawl exports and Search Console samples.

Source: Google sitemap guidance Related: GSC monitoring runbook

Diagnostic step	Question to answer	Action when it fails
Fetched URL	Did the request resolve to the URL you meant to test?	Fix redirects or test the final destination directly.
Declared canonical	Does the HTML declare one intended canonical?	Remove duplicate tags and rebuild template output.
Canonical target	Does the target return 200 without noindex or redirects?	Make the target indexable or point to the correct final URL.
GSC sample	Does Google select the same canonical for priority pages?	Log mismatches in the worksheet before requesting recrawl.

Why this matters during a rebuild

A canonical tag is only useful when it agrees with redirects, sitemaps, internal links, robots directives, and the final URL Google can crawl. After a WordPress to Next.js migration, copied canonicals and redirecting canonical targets are two of the easiest mistakes to miss.

When one URL is not enough

Use the checker for spot checks and priority URLs. For a migration, pair it with the canonical issue worksheet so you can track every page, sitemap row, redirect, internal-link target, and Google-selected canonical together.