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What Is a Canonical URL?
A canonical URL is the preferred URL for a page when multiple URLs serve the same
or very similar content. The <link rel="canonical"> tag tells
search engines which URL to index and attribute link equity to.
Without canonicalization, duplicate content can split ranking signals across
multiple URLs, reducing SEO effectiveness.
Common Duplicate URL Scenarios
| Duplicate URL | Canonical |
|---|---|
| http://example.com/page | https://example.com/page |
| https://www.example.com/page | https://example.com/page |
| https://example.com/page/ | https://example.com/page |
| https://example.com/page?utm_source=email | https://example.com/page |
| https://example.com/page?sort=asc | https://example.com/page |
Implementing Canonical Tags
<!-- In the <head> section -->
<link rel="canonical" href="https://example.com/page">
<!-- Self-referencing canonical (recommended on all pages) -->
<link rel="canonical" href="https://example.com/current-page">
<!-- Cross-domain canonical (syndicated content) -->
<link rel="canonical" href="https://original-site.com/article">
Every page should have a self-referencing canonical tag, even if there are no duplicates. This prevents search engines from creating their own canonical interpretation of your URLs.