Canonical Tags

Duplicate content problem

The same content can live at multiple URLs: example.com/page, www.example.com/page, example.com/page?utm=tracking, etc. Search engines see these as separate pages, splitting ranking power. Canonical tags tell Google which is the preferred version.

Canonical tag example

Place the canonical tag in the <head> of every duplicate. Point all variants to the primary URL.

<!-- On page: example.com/article?id=123&utm_source=newsletter -->
<head>
  <link rel="canonical" href="https://example.com/article/123">
</head>

<!-- On page: www.example.com/article/123 -->
<head>
  <link rel="canonical" href="https://example.com/article/123">
</head>

<!-- All URLs point to the same canonical -->
<!-- Ranking power consolidates on example.com/article/123 -->

Self-referential canonicals

Every page can have a canonical tag pointing to itself. This is optional but clarifies which version is the primary. Helpful for large sites.