Duplicate content is unavoidable on most sites — print views, filters, tracking parameters. Canonical tags tell search engines which URL is the one to index.
What a canonical looks like
<link rel="canonical" href="https://example.com/widget" />Each indexable page should have exactly one canonical pointing to itself (self-referencing) or to a better version.
Self-referencing matters
A page should include a canonical pointing to its own URL. It sounds redundant, but it consolidates signals and prevents accidental duplicates from variants.
Common uses
- Paginated series: each page self-canonicals (do not point page 2 at page 1)
- Filtered/sorted URLs: canonical to the base category
- Tracking parameters: canonical to the clean URL
- Syndicated content: canonical to the original
Absolute vs relative
Use absolute URLs (https://…). Relative canonicals are error-prone, especially across subfolders.
Canonical is a hint
Google may ignore it if other signals disagree. Pair canonicals with consistent internal links and use noindex where appropriate.
Check yours
Paste a page's HTML into the free canonical URL checker to confirm the canonical, title and description are correct — no signup needed.