Canonical tag checker for duplicate and conflicting pages
Filters, tracking parameters, print versions and http/https copies can turn one page into ten URLs. If canonical tags are missing or point to the wrong place, search engines may pick a version you did not want. This prompt has your agent read the canonical tag on each page and check it against redirects, noindex and your sitemap.
The prompt
- Audit the canonical tags on [WEBSITE]. Check [PAGES TO CHECK]. For each page, read the rel="canonical" in the HTML and in the HTTP header, and report: missing canonicals, canonicals pointing to a different URL, canonicals to pages that redirect, 404 or are noindexed, relative URLs, more than one canonical tag, http vs https or www mismatches, and canonical URLs not listed in the sitemap. Also test these URL variations: [URL VARIATIONS]. Tell me which version of each page search engines are likely to treat as the main one, and why. Save the results as an Excel file with a "fix" column and add a one-page summary in plain English.
What to change
- [WEBSITE]: Your site, e.g. "lumenhome.co".
- [PAGES TO CHECK]: e.g. "all pages in the sitemap", "the 200 product pages" or attach a list of URLs.
- [URL VARIATIONS]: e.g. "?color= filters, ?utm_ tracking, /page/2 pagination", or write "the usual ones".
Example result
- Canonical tag audit · lumenhome.co (example)
- Pages checked: 380 from the sitemap, plus 60 URL variations
- Summary
- • 338 pages OK: one self-referencing, absolute canonical
- • 18 canonicals point to a URL that redirects (old /products/ path)
- • 11 pages have no canonical tag
- • 7 pages have two canonical tags (theme + SEO plugin)
- • 6 canonicals point to a noindex page
- Fix first
- • Two canonicals on blog posts: the theme adds one and the SEO plugin adds another, and they disagree on the trailing slash. Turn off the theme tag.
- • Old path: /products/oak-lamp has canonical → /products/oak-lamp, but that URL now 301s to /shop/oak-table-lamp. Update the canonical to the final URL.
- URL variations tested
- • /shop/oak-table-lamp?color=black → canonical /shop/oak-table-lamp · OK
- • /shop/oak-table-lamp?utm_source=newsletter → canonical /shop/oak-table-lamp · OK
- • /blog/page/2 → canonical /blog · Problem: page 2 should canonicalize to itself, or its posts may be missed
- • http://lumenhome.co/about → 301 to https · OK
- Rules of thumb used
- • Each indexable page points its canonical to itself, using the full https URL
- • Duplicates (filters, tracking, print views) point to the main version
- • The canonical URL returns 200, is indexable and is in the sitemap
- • Canonicals are hints: links, sitemaps and redirects should all agree with them
How to do it with todo.is
- Copy the prompt, add your site and which pages to check.
- Paste it into todo.is or send it to your agent on Slack or Telegram.
- Your agent opens each page, reads the canonical in the code and headers, and tests the variations.
- Fix the rows marked in the Excel file, then ask your agent to re-check only those pages.
Tips for a better result
- Most canonical problems come from two tools adding tags at once. Check your theme, SEO plugin and any app that edits the head.
- Paginated pages (page 2, 3…) should usually point to themselves, not to page 1.
- Keep canonicals, internal links and the sitemap pointing to the same URL. Mixed signals are why Google sometimes picks another version.
- After a domain or URL change, re-run this check. Old canonicals are easy to miss.
canonical tag checker: FAQ
- What does a canonical tag do? It tells search engines which URL is the main version of a page when several URLs show the same or very similar content. It is a strong hint, not a command.
- Should every page have a self-referencing canonical? It is a good default for indexable pages. It protects you when tracking or filter parameters create extra URLs.
- Why does Google ignore my canonical tag? Usually because other signals disagree, like internal links, redirects or the sitemap pointing elsewhere, or because the pages are not really duplicates. Search Console shows the canonical Google chose.
- Can todo.is see what Google chose as the canonical? It checks your pages directly. If you export the Page indexing report from Search Console and attach it, your agent compares your canonicals with Google's choice.
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