canonical
A declaration of which URL is the preferred version.
What canonical does not show
A canonical pointing away from a page is a request not to index that page, and a sitemap declaring a URL whose canonical points elsewhere is a contradiction the site is publishing about itself.
How CrawlCheck measures canonical
2 finding codes measure it. Each one’s share of all scans is computed from the live corpus when this page is served, not typed into it.
| Finding code | Share of scans | Guide |
|---|---|---|
HOST_DUPLICATE_200 | 6.2% | Canonical URL audit: do tags, redirects and sitemap agree? |
DOMAIN_IS_ALIAS | 0.9% | Canonical URL audit: do tags, redirects and sitemap agree? |
Every code, its rule and its current rate: the dataset page. Scan a site to see which apply to it.
Where canonical comes up on this site
- Canonical URL audit: do tags, redirects and sitemap agree?The canonical tag declares the one address a site wants treated as the page, and most audits check only that the tag exists.
- www and non-www both return 200? A canonical won't fix itWhy does a correct canonical not solve it?
- Do AI crawlers render JavaScript? Check what they seeThe same goes for canonical tags, meta robots and hreflang: a directive that only exists after hydration is one most clients never receive.
- How to write an llms.txt and check it is actually servedBuild the file from your sitemap rather than your navigation: the sitemap holds each page’s canonical address, the navigation holds whatever humans click.
- XML sitemap audit: check the file and every URL in itIt is healthy when its bytes parse and every entry expresses the same canonical plan as the site it describes.
Terms this definition uses
Definitions that name canonical
faceted navigation · Sitemap · Sitemap hreflang · Canonical cluster · 308 redirect · canonical URL · host duplicate · duplicate content · apex domain · canonical origin · Link header
Related terms in Indexing and discovery
Whether a page can be found and kept, separately from whether it can be fetched.
nosnippet · max-snippet · max-image-preview · unavailable_after · noimageindex · index coverage · noindex · X-Robots-Tag · orphan page · E-E-A-T · E-E-A-T proxies · topical authority · Soft 404 · case consistency · accessibility structure · landmark region · accessible name · skip link · main landmark · alt attribute · form control name · duplicate id · IndexNow · faceted navigation · thin content · duplicate content · near-duplicate · boilerplate · MinHash · shingle · dead anchor · placeholder content · image placeholder · alt text · EXIF
Questions about canonical
What is canonical?
A declaration of which URL is the preferred version.
What does canonical not show or guarantee?
A canonical pointing away from a page is a request not to index that page, and a sitemap declaring a URL whose canonical points elsewhere is a contradiction the site is publishing about itself.
How does CrawlCheck measure canonical?
Through the finding codes HOST_DUPLICATE_200, DOMAIN_IS_ALIAS, each with a stated rule, evidence bytes and a live share of scans on the dataset page.
Which area of the glossary does canonical belong to?
Indexing and discovery: Whether a page can be found and kept, separately from whether it can be fetched.
← index coverage · noindex →
See it in the full glossary · 772 terms across 19 areas.
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