What is Canonical URL?
A canonical URL is the main version of a page that you want search engines to index and rank when several URLs show the same or very similar content.
You set it with a rel="canonical" link tag in the page head, or through HTTP headers for files like PDFs. The tag points from each duplicate to the main page, and the main page usually points to itself.
Google treats the canonical tag as a strong hint, not a command. It also looks at redirects, internal links, sitemaps and HTTPS when deciding which URL to show.
How to add a canonical tag
The most common method is a link element in the page head. Every page should usually have a self referencing canonical pointing to its own clean URL.
<!-- On https://example.com/shoes/?color=red --> <link rel="canonical" href="https://example.com/shoes/" /> <!-- Self referencing canonical on the main page --> <link rel="canonical" href="https://example.com/shoes/" />
For PDFs and other non HTML files, you can send the canonical in an HTTP header instead: Link: <https://example.com/guide/>; rel="canonical".
Canonical signals Google uses
A canonical tag is a strong hint, not a command. Google looks at several signals together and may choose a different canonical if they conflict.
| Signal | Strength | Tip |
|---|---|---|
| 301 redirects | Strong | Best when the duplicate does not need to exist |
| rel=canonical tag | Strong hint | Use absolute URLs and point to an indexable page |
| Internal links | Supporting | Always link to the canonical version |
| XML sitemap | Weak | List only canonical URLs |
| HTTPS and clean URLs | Tie breaker | Google prefers secure, simple URLs |
Common canonical tag mistakes
Canonical to a redirected or 404 page
The target must return a 200 status and be indexable.
Mixing canonical and noindex
Sending both signals confuses Google. Choose one approach for each page.
Every page canonical to the home page
This tells Google most of your pages are duplicates and can drop them from the index.
Paginated pages canonical to page one
Each page in a series should usually canonical to itself so deeper items stay discoverable.
Relative URLs and http versions
Use full absolute HTTPS URLs to avoid errors.
Ignoring "Google chose different canonical"
Check this Search Console status and fix the conflicting signals behind it.
Why canonical URLs matter
A canonical URL is the preferred version of a page when several URLs show the same or very similar content. Search engines use the canonical tag, redirects, internal links and sitemaps to decide which URL to index and rank. Clear canonicals consolidate signals into one page and avoid duplicates competing.
Common cases include URL parameters, product variants, HTTP and HTTPS versions, trailing slashes and syndicated content.
Canonical setup steps
- 1Add a self referencing canonical to every indexable page.
- 2Point duplicates to the main version.
- 3Use absolute URLs.
- 4Keep canonicals consistent with internal links and sitemaps.
- 5Avoid canonicals to redirected or noindexed pages.
- 6Check Google's chosen canonical in URL Inspection.
Canonical mistakes
Canonical to the home page
Pointing many pages to the home page confuses search engines.
Conflicting signals
Canonical says one URL, sitemap lists another.
Paginated pages to page one
Each paginated page should usually be self canonical.
Canonical checklist
- 1Self canonical on indexable pages.
- 2Duplicates point to the main URL.
- 3Canonicals match sitemaps.
- 4No canonicals to redirects.
- 5Google's choice checked.
Cross domain canonicals
Publishers syndicating articles can ask partners to add a canonical pointing to the original. This helps Google credit the original source.
Why Canonical URL matters for SEO
Canonicals consolidate ranking signals. Links and engagement spread across duplicate URLs are combined onto the main page, which gives it a better chance to rank.
They also keep search results clean and save crawl budget on large sites with filters, tracking parameters or printer friendly pages.
How Canonical URL works
Canonical tags are used in a few common situations.
URL parameters
Filter, sort and tracking parameters create many URLs for one page. A canonical points them all to the clean version.
Similar product pages
Products in several colours or categories can canonicalise to one main product URL.
Syndicated content
When another site republishes your article, a cross domain canonical tells Google yours is the original.
An online shoe store has /running-shoes, /running-shoes?sort=price and /running-shoes?colour=blue. Adding a canonical from the sorted and filtered versions to /running-shoes stops three versions competing and helps the main category page rank.
Canonical URL checklist
- ✓Add a self referencing canonical to every indexable page
- ✓Use absolute URLs with HTTPS
- ✓Point canonicals only to pages that return 200 status
- ✓Keep canonical, sitemap and internal links consistent
- ✓Avoid canonical chains
- ✓Check the URL Inspection tool to see the canonical Google chose
Common Canonical URL mistakes
Canonicalising to a redirect or 404
Google may ignore the tag if it points to a broken or redirected URL.
Mixing noindex and canonical
Sending both signals confuses search engines.
Canonicalising all pages to the homepage
This tells Google every page is a duplicate and can remove them from the index.
Conflicting signals
Internal links and sitemaps pointing to non canonical URLs weaken the hint.
Related SEO terms
Canonical URL FAQs
What does a canonical tag look like?
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It is a link element in the page head, such as <link rel="canonical" href="https://example.com/page/">.
Should every page have a canonical?
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Yes. A self referencing canonical on each indexable page is a good default.
Do canonicals work across domains?
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Yes. Cross domain canonicals are useful for syndicated content.
Is a canonical tag a directive?
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It is a strong hint. Google may choose a different canonical if other signals disagree.
Should canonical tags include parameters?
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Usually not. Canonicals should point to the clean, preferred URL.
Is a canonical tag the same as a redirect?
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No. A redirect sends users and bots to another URL, while a canonical keeps both URLs live but tells Google which to index.
Can Google ignore my canonical?
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Yes. If other signals strongly suggest a different URL, Google may choose its own canonical.
How do I check which canonical Google picked?
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Use the URL Inspection tool in Search Console, which shows the user declared and Google selected canonical.
Do canonicals pass link value?
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Signals from duplicates are usually consolidated to the canonical URL.
Do canonicals affect AI crawlers?
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Many crawlers respect canonicals, which helps them focus on the main version.