Canonical Tag
HTML tag declaring the preferred URL for duplicate content.
A canonical tag (<link rel="canonical" href="...">) is an HTML element that tells search engines which version of a URL is the authoritative one when the same or near-identical content is reachable from multiple URLs. The canonical receives the indexing signals; the duplicates are consolidated to it.
Why the canonical tag matters
Without canonicals, sites with filterable listings, paginated archives, query parameters, AMP variants or syndicated content end up with multiple URLs serving the same content. Google may pick the wrong one as canonical, may split ranking signals across versions, or may flag pages as "Duplicate, Google chose different canonical than user" in Search Console.
How canonical tags should be set
- Every indexable page should have a self-referencing canonical pointing to the clean URL it wants ranked.
- Trailing slashes, protocol (HTTPS) and domain capitalisation must match.
- Cross-domain canonicals are honoured but require both sides to be reachable and consistent.
- The canonical should not point to a URL that 404s, redirects, or is blocked by robots.
Common canonical mistakes in UK financial sites
Filterable benchmark and case-study libraries are the worst offenders. Niche or product filters create dozens of URL variants of the same page; without a canonical pointing to the parent, Google sees them as duplicates and silently drops most of them.
Related terms
- Duplicate Content
- Indexing
- Robots.txt
- llms.txt