Canonical URL
A canonical URL tells Google which version of a page is the original when multiple URLs show the same content. It prevents duplicate content problems.
A canonical URL is a tag in your page's code that tells Google, "This is the real version of this page." It solves a surprisingly common problem: the same content showing up at multiple web addresses.
Your homepage might be reachable at example.com, www.example.com, example.com/index.html, and example.com/?ref=facebook. To you, that's one page. To Google, those are four different pages with identical content. Without a canonical tag, Google has to guess which one matters. Sometimes it guesses wrong.
Why It Matters for Your Business
Duplicate content confuses Google. When it finds the same content at multiple URLs, it has to pick one to show in search results. It might pick the wrong one, or it might split the ranking power between them so none of them rank well.
For small business websites, this often happens without anyone realizing it. URL parameters from ad campaigns, trailing slashes, HTTP vs. HTTPS versions, and www vs. non-www versions all create duplicates. A canonical tag points Google to the one URL you want to rank.
The Basics
It's a single line of HTML. A canonical tag looks like <link rel="canonical" href="https://example.com/your-page" /> in the <head> section of your page. It tells Google that the specified URL is the authoritative version.
Every page should have one. Even if a page only exists at one URL, add a self-referencing canonical tag. This is a safety net that prevents future issues if duplicate URLs get created by accident.
It's a hint, not a command. Google usually follows canonical tags, but it can override them if it thinks the tag is wrong. For example, if your canonical points to a page that returns an error, Google will ignore it.
Redirects are stronger. If you have a true duplicate that should never be visited, a 301 redirect is better than a canonical tag. Canonical tags are best for situations where both URLs need to exist but only one should rank.
FAQ
What happens if I don't set a canonical URL?
Google picks a version on its own. Sometimes it picks right. Sometimes it picks the URL with tracking parameters or the HTTP version instead of HTTPS. You lose control of which URL shows up in search results, and your ranking power can get diluted across multiple URLs.
How do I check if my pages have canonical tags?
Right-click on any page in your browser, select "View Page Source," and search for "canonical." You should find a link tag with rel="canonical" that points to the correct URL for that page. You can also use Google Search Console to check for canonical issues under the "Pages" report.
What's the difference between a canonical tag and a redirect?
A redirect sends visitors and Google from one URL to another. The old URL stops working. A canonical tag keeps both URLs working but tells Google which one to show in search results. Use redirects when a page has permanently moved. Use canonicals when both URLs need to stay active.