Canonicals & Duplicate Content
When similar or identical content lives on multiple URLs, Google may not know which to rank. Canonical tags solve this.
The duplicate content problem
Duplicate content happens with URL parameters, print versions, http vs https, trailing slashes, and similar product variants. It splits ranking signals and wastes crawl budget.
The canonical tag
A canonical tag (rel="canonical") tells Google which URL is the “master” version to index and rank. Point duplicates at the preferred URL to consolidate signals.
Pro tips
- Every page should have a self-referencing canonical by default.
- Use canonicals, not noindex, for near-duplicate variants you still want accessible.
- Keep canonicals consistent with your sitemap and internal links.
Common mistakes
- Canonicalising every page to the homepage (a common, harmful bug).
- Conflicting signals: canonical to one URL but linking to another.
- Relying on canonicals to fix truly thin or duplicate pages that should be merged.
Summary
Duplicate content splits your ranking signals. Canonical tags declare the master URL so Google consolidates and ranks the right page.