Canonical URLs

Which address is the "official" one when the same content lives at several URLs

📖 Detailed description

Canonical URLs solve the problem of the same content being available at several different addresses. They tell Google which address is the "official" one and should be shown in the results.

A real-world example: you run a store and the same product can be reached through /products/t-shirt, /promotions/t-shirt, and /new/t-shirt. To Google, those are three different pages with identical content - it does not know which one to show and may even see it as an attempt to game the system!

The canonical tag says: "Hey Google, no matter where you found this content, the official address is this one." As a result, all of your "SEO power" is concentrated on a single URL instead of being spread across several.

Most common problems

Duplicate content

Google does not know which version to show

Diluted links

Different pages link to different versions

Duplicate penalties

Google may lower your ranking for copied content

www / non-www issues

For Google, those are different addresses too

How to fix it?

Add a canonical tag on every page pointing to the official version

Pick a single version: www or non-www, http or https

For duplicates, point to the original page

Use canonical tags for your mobile version as well

Check that the canonical points to a working address

Examples

Good example

Bad example

The same product at 5 different addresses with no canonical

🔗 Related indicators

📱

Mobile friendliness

Does your site work well on a phone? That is how most people view it!

🤖

Robots.txt and Sitemap

A map and a set of instructions telling Google how to navigate your site

🚀

Core Web Vitals

Google's three scores that measure the real experience of using your site

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