If you manage a website with lots of pages, blog content or product listings, there’s a good chance some of it overlaps. You might have similar pages with near-identical content, or different URLs that show the same product. Search engines don’t love that and it can hurt your rankings.
That’s where canonical tags come in.
In this guide, we’ll explain what canonical tags are, why they matter, and how to use them properly to keep your SEO on track.
What is a canonical tag?
A canonical tag is a simple piece of HTML code that tells search engines which version of a page is the “main” one. It looks like this:
<link rel="canonical" href="https://www.example.com/main-page" />
When placed in the <head> of a page, it points to the preferred version that should be indexed and ranked. This helps avoid confusion when you have duplicate or very similar content across multiple URLs.
Why do canonical tags matter?
Search engines want to avoid indexing duplicate content. If they find multiple pages with the same or very similar content, they may:
- Struggle to decide which one to rank
- Split ranking signals between versions
- Pick the wrong page to show in search results
Using canonical tags helps you:
- Consolidate SEO value to one page
- Avoid ranking issues caused by duplicates
- Control which version appears in search results
It’s a small step with big impact especially for eCommerce sites, blogs, and platforms with dynamic URLs.
When should you use a canonical tag?
Here are a few common situations where canonical tags are useful:
- Similar products or pages
You might have product variants (e.g. colour or size) that each live on separate URLs, but the descriptions are mostly the same.
Set the main product page as canonical to avoid diluting ranking signals.
- Sorting and filtering options
Pages generated through filters (like ?sort=price) often duplicate the original content.
Use a canonical tag pointing to the unfiltered version.
- Content reuse across categories
If a blog post is listed under multiple categories or tags with unique URLs, choose the main one and apply a canonical tag to others.
- HTTP vs HTTPS or www vs non-www
If both versions of your site are accessible, canonical tags can help indicate your preferred version to search engines (though ideally this should also be handled via redirects and Search Console settings).
How to add canonical tags
Most content management systems (like WordPress, Shopify or Webflow) have built-in options or plugins to manage canonical tags. You can usually:
- Set the canonical URL manually in the page settings
- Let the system default to the page’s own URL (self-referencing)
- Use SEO plugins like Yoast or RankMath to configure easily
For custom-built websites, your developer can add the tag directly to the <head> section of each page.
Best practices for canonical tags
- Always use the full, absolute URL in your canonical tag (including
https:// and domain name)
- Use only one canonical tag per page. Multiple tags can confuse search engines.
- Make sure the canonical version exists and loads correctly. Don’t point to broken or redirected pages.
- Avoid using canonical tags as a fix for thin or poor content. They should support a clean structure, not cover up quality issues.
- Pair with other tools like 301 redirects and hreflang when needed, especially on international or multilingual sites.
Common mistakes to avoid
- Pointing all pages to the homepage or a generic landing page
- Adding a canonical tag but not updating it when the URL structure changes
- Using the tag inconsistently across duplicated content
- Forgetting to test the implementation after changes
These issues can stop canonical tags from working as intended or worse, create new problems with how pages are indexed.
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Final thoughts
Canonical tags might seem technical, but they play a key role in helping search engines understand your site. When used correctly, they keep your content focused, your rankings stronger, and your site structure cleaner.
If you’re not sure whether your website is using canonical tags properly, it’s worth taking a look. Even small adjustments can help search engines better interpret your content and improve overall site performance.
