How to Check Canonical Tags Across Your Entire Site
A canonical tag tells search engines which page to index. Get it wrong and you suppress pages from Google. Here is how to audit canonical tags properly.
13 May 2026 · 5 min read
A canonical tag tells search engines which version of a page is the "official" one to index. Get it wrong and you can accidentally suppress pages from Google's index, consolidate ranking signals to the wrong URL, or create conflicting signals that leave Google guessing.
Checking canonical tags across an entire site - not just one page at a time - is where most audits fall short. Here is how to do it properly.
What canonical tags do
A canonical tag is an HTML link element in the <head> of a page:
<link rel="canonical" href="https://www.example.com/target-page/" />
It tells search engines: "Even if you reached this page via a different URL, treat this href as the definitive version." Any ranking signals accumulated by the page - links, content authority - are consolidated to the canonical URL.
Common reasons to use a canonical tag:
- Duplicate content from URL parameters - filtering or sorting URLs like
/products?sort=priceoften produce identical content to/products. The canonical points to/products. - HTTP/HTTPS or www/non-www duplicates - if your site is accessible at multiple root URLs, canonicals ensure only one version is indexed.
- Paginated content - deciding which page in a paginated series to treat as canonical.
- Syndicated content - if your content is published elsewhere, a canonical back to your original URL consolidates signals.
Common canonical tag problems
Self-referencing canonicals (correct)
A page at https://www.example.com/page/ with a canonical pointing to https://www.example.com/page/ is correct. Most pages should have a self-referencing canonical.
Canonical pointing to a different URL (intentional or a mistake)
A page that is intentionally non-canonical points its canonical to another URL. This is correct if the page is genuinely a duplicate. It is a problem if the page was supposed to be canonical - for example, a paginated page whose canonical was accidentally set to page 1 rather than its own URL.
Missing canonical
No canonical at all is not necessarily wrong, but it leaves search engines to infer the canonical themselves. On sites with URL parameter variations, this can lead to incorrect canonicalisation.
Canonical chain
Page A canonicals to page B, which canonicals to page C. Like redirect chains, canonical chains add unnecessary complexity and can confuse crawlers. The canonical should always point to the final destination.
Canonical pointing to a non-indexable page
A canonical that points to a URL blocked by robots.txt or carrying a noindex tag is counterproductive. The canonical signal reaches a page that cannot be indexed, which means neither the source nor the target ends up indexed.
Canonical pointing to a 404 or redirect
A canonical pointing to a broken or redirecting URL sends confusing signals. Google may consolidate authority to a URL that no longer exists, or follow the redirect to an unintended destination.
How to check canonical tags at scale with Crawly
Checking canonical tags one URL at a time is not practical on a site with hundreds or thousands of pages. Crawly crawls the entire site and records the canonical tag for every page it finds.
1. Run a full crawl
Open Crawly, click New Crawl, and enter the root URL. Let the crawl complete. Crawly will visit every page reachable via internal links and record the canonical tag alongside all other metadata.
2. Filter for non-canonical pages
In the Pages tab, filter by Non-indexable. Among the results, look for pages flagged as "Has canonical to another URL". These are pages that declare a canonical pointing elsewhere. Review each one:
- Is this page intentionally non-canonical?
- Does the canonical URL it points to actually exist and return a 200?
- Is the canonical URL itself indexable?
3. Check for canonical chains
Crawly flags pages where the canonical points to a URL that itself has a canonical pointing somewhere else. These are canonical chains. The fix is to update the first page's canonical to point directly to the final destination.
4. Check for canonicals pointing to broken URLs
In the Issues tab, look for pages with canonical targets that return 4xx or are redirecting. This is an indirect check - Crawly records the canonical href and whether the target URL is crawled. Compare the two to identify mismatches.
5. Check self-referencing canonicals on key pages
For your most important pages - homepage, key landing pages, category pages - confirm that the canonical is present and self-referencing. If a key page has no canonical, add one.
How to check a single canonical tag
For spot-checking individual pages, use Crawly's Canonical Tag Checker. Enter a URL and it fetches the page and returns:
- The canonical href value
- Whether the tag is present
- Whether it is self-referencing or pointing to a different URL
This is useful for quickly verifying a page after a fix, or for checking a specific URL without running a full crawl.
Canonical tags and hreflang
On international sites, canonical and hreflang tags interact. The canonical should point to the language/region-specific version of the page, not a generic default. For example, a French page should have a canonical pointing to the French URL, and hreflang tags pointing to the equivalents in other languages.
A common mistake is setting all language variants to the same canonical, which effectively tells Google to ignore all but one.
Crawly surfaces hreflang issues as a separate audit category. If you have an international site, check both canonical and hreflang data together.
After fixing canonical issues
Once you have updated canonical tags, run a new crawl and use Crawly's crawl comparison to verify that the issues are resolved. The comparison diff will show which pages changed their canonical status between crawls.
Submit updated pages to Google Search Console for re-crawling if you have made significant changes to high-priority pages.
Canonical tag errors are easy to overlook and slow to correct once they have affected indexation. Regular audits catch them early. For a full walkthrough of running a technical SEO audit that covers canonicals alongside every other on-page signal, see the technical SEO audit guide.
Download Crawly and check your canonical tags across the entire site in one crawl.