# Canonical Tags — SEO for Developers Source: https://www.geekswithgeeks.com/en/seo-developers/seo-canonical-tags > Prevent duplicate content issues with canonical URL declarations. ## 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 `` of every duplicate. Point all variants to the primary URL. ```html ``` ## 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.