Canonical URLs: Prevent Duplicate Content

What Is a Canonical URL?

A canonical URL tells search engines which version of a page is the "main" one. This prevents duplicate content issues when the same content is accessible at multiple URLs.

When You Need Canonical Tags

- **www vs non-www** — example.com and www.example.com

- **HTTP vs HTTPS** — http:// and https:// versions

- **Trailing slash** — /page and /page/

- **Query parameters** — /products and /products?sort=price

- **Syndicated content** — Content republished on other sites

How to Add

<head>

  <link rel="canonical" href="https://yoursite.com/page">

</head>

Common Mistakes

1. **Missing canonical** — Every page should have one, pointing to itself

2. **Canonical to a 404 page** — Don't point to pages that don't exist

3. **Canonical doesn't match og:url** — These should be the same URL

4. **HTTP canonical on HTTPS page** — Always use HTTPS in canonical

5. **Relative URL** — Always use absolute URL with protocol

Self-Referencing Canonicals

Even if a page has no duplicates, add a self-referencing canonical:

This is a best practice recommended by Google.

Check your canonicals with [SEO Snapshot](/) — we verify canonical exists, check for protocol mismatches, and compare with og:url.

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