Canonical Tag
An HTML element that tells search engines which version of a page is the "original" when duplicate or near-duplicate versions exist. Prevents diluted rankings from duplicate content.
Why It Matters
Duplicate content is more common than most people think. URL parameters, print versions, HTTP vs HTTPS, www vs non-www, pagination - all of these can create multiple URLs serving the same content. Without canonical tags, Google has to guess which version to rank. It often guesses wrong.
Canonical tags give you control. They tell Google: "I know this content exists at multiple URLs, but this is the one I want you to rank." The alternative is watching your ranking signals get split across duplicate URLs, with none of them performing as well as a single consolidated page would.
In Practice
Every page should have a self-referencing canonical tag pointing to its own URL. This is your baseline. Then use canonical tags specifically for:
Product pages with URL parameters (colour, size, sort order). Syndicated content that appears on your site and a partner's. Paginated content where page 2, 3, etc. should point to page 1. Mobile and desktop versions if you're not on responsive design.
Audit your canonicals regularly. A misconfigured canonical tag - like accidentally canonicalising all pages to the homepage - can be devastating. Use Google Search Console's Index Coverage report to spot canonical issues.
Common Mistakes
Canonicalising pages to the wrong URL. Using relative URLs instead of absolute in canonical tags. Setting canonical tags on pages that are also blocked by robots.txt (contradictory signals). Forgetting that canonical is a hint, not a directive - Google can ignore it.
Related Terms
Glossary
Duplicate Content
The same content appearing on multiple URLs - confuses Google about which to rank.
Glossary
Redirect (301 vs 302)
301 is permanent (transfers ranking signals), 302 is temporary - use the right one.
Glossary
Indexing
Adding a crawled page to Google's database so it can appear in search results.
Glossary
Technical SEO
Optimising your site's infrastructure so search engines can crawl, render, and index it.
Know the Words.
Now See Them in Action.
Free teardown. No jargon. Just what's broken and how to fix it.
Get The Teardown