Canonicalisation

Canonicalisation in plain English

Canonicalisation is the process of choosing the representative URL from a group of pages with the same or very similar content. Google does this itself, using signals such as redirects, canonical tags, internal links and sitemaps. Site owners influence the choice by sending clear, consistent signals. Google's canonicalisation guide explains how it works.

How to check canonicalisation on your site

Use Search Console's URL Inspection tool to compare "User-declared canonical" with "Google-selected canonical" for important pages. Where they differ, look for conflicting signals: internal links, redirects, sitemap entries and hreflang. Fix the signals rather than adding more tags.

A worked example

A shoe shop's internal links point to product URLs with a trailing "?ref=menu", its canonical tags point to the clean version, and its sitemap lists a third version with capital letters. Google picks inconsistently. Aligning all three on one clean URL settles it.

Where it usually goes wrong

• Relying on one signal while others point elsewhere.
• Canonicalising pages that aren't really duplicates.
• Linking internally to non-canonical versions.
• Expecting changes to be picked up instantly. Google needs to recrawl.

Why a small site should care

When signals conflict, Google may pick a different URL from the one you want, such as a version with tracking parameters or the HTTP version. That can make reports confusing and split the value of links. Consistent signals are a simple way to avoid it.

It's especially common on shops, booking systems and sites with tracking parameters on links. The fix is rarely a single tag. It's making redirects, internal links, sitemaps and canonical tags all agree with each other.

Connected technical terms

• Canonical URL: The preferred URL for duplicate or similar content, declared with rel=canonical.
• Duplicate content: Same or near-identical content on multiple URLs.
• Redirect: Sending users and crawlers from one URL to another.