Glossary
What is a canonical tag?
A canonical tag is a line of HTML in a page’s head, written as <link rel="canonical" href="…">, that tells search engines which URL is the preferred version of a page when the same or very similar content is available at more than one address.
Also called rel=canonical, canonical URL
Why duplicate URLs happen
The same page can often load at several addresses: with and without “www”, with and without a trailing slash, with tracking parameters such as ?utm_source=, or through filters and sorting on a listing. To a search engine, each address can look like a separate page with the same copy.
The canonical tag was introduced in 2009 by Google, Yahoo and Microsoft to solve this. It points every copy to one main URL, so ranking signals such as links are combined there instead of being split.
Why it matters for B2B websites
B2B sites collect duplicates quietly: campaign links with parameters, the same case study under two categories, a staging copy that got indexed, or an old and a new URL living side by side after a redesign. Without clear canonicals, search engines may show the wrong version, or spread your page’s strength across several URLs.
A hint, not an order
Google treats the canonical tag as a strong hint. It can choose a different canonical if other signals disagree, for example if internal links, the sitemap and redirects all point somewhere else. Consistency is what makes the tag work.
Common mistakes
- Every page pointing its canonical to the home page
- Canonicals pointing to URLs that redirect or return a 404
- A page listed in the sitemap but canonicalized to another URL
- Using a canonical where a 301 redirect is the right tool, such as a page that has moved for good
- Relative URLs or the wrong protocol (http instead of https)
How we handle it
Every page we build carries a self-referencing canonical with the full https URL, generated by the page template, and the sitemap lists only canonical URLs. During a website migration we check that canonicals, redirects and internal links all agree before launch.
Last updated 15 November 2026
