When a website has more than one page with almost the same content, search engines can get confused about which page should rank. Canonical tags work like a signboard that says, “This is the main page to follow.” By using them correctly, you prevent duplicate content issues, protect your rankings, and make life easier for both users and search engines. In this blog, we’ll explore why canonical tags matter and how to use them the right way.
What Is a Canonical URL?
A canonical URL is like choosing one “main copy” of a page when you have multiple versions that look the same. Think of it like having five photos of the same shoe — you only want to show Google which one is the official picture.
For example, www.site.com/shoes and www.site.com/shoes?color=red might show the same content, but by marking www.site.com/shoes as canonical, you guide search engines to focus on the right page. This keeps your website organised and your rankings strong. Avoids duplicate content issues, ensures rankings aren’t split, and clearly defines which page deserves visibility.
What is a canonical tag?
When a search engine visits your website, it looks at every page to decide which one to show in search results. If it finds multiple pages with the same or very similar content, it needs to choose one. A canonical tag (rel=”canonical”) is like a label that tells search engines which page is the main one when two or more pages look almost the same. For example, if your website has these pages:
- https://example.com/pizza
- https://example.com/pizza?size=large
- https://example.com/pizza?ref=homepage
All of them show the same pizza content, but you only want Google to treat /pizza as the main page. That’s when a canonical tag helps.
Example:
- /pizza has the main content.
- /pizza?size=large has a canonical tag pointing to /pizza.
Google knows to show /pizza in search results, while still counting the link value from /pizza?size=large.
In simple words: it’s like telling Google, “Only show this page, but don’t ignore the other pages’ votes.”
If you don’t use it, Google might get confused about which page to show in search results.
For example, these two pages may look alike:
- https://example.com/pizza
- https://example.com/pizza?size=large
By adding a canonical tag on the second page, you’re saying, “The real page to focus on is /pizza.”
Here’s how the code looks in the <head> section of a webpage:
<link rel=”canonical” href=”https://example.com/pizza/” />
Using canonical tags keeps your website clean, avoids duplicate content issues, and helps search engines show the right page.
Why Canonical Tags Matter for SEO
Canonical tags are important because they help avoid duplicate content issues, which can negatively impact your rankings. If Google finds multiple similar pages, it may:
- Reduce visibility in search results
- Split backlinks between versions
- Waste crawl budget
- Slow down the indexing of fresh content
Google has confirmed it uses around 40 different signals to decide which page is canonical. That means canonical tags are essential, but not the only factor in determining the rankings. Things like internal linking, sitemaps, redirects, and even how users engage with your pages also matter.
Example:
A blog has the same article at /blog/seo-tips and /blog/seo-tips?ref=newsletter. A canonical tag pointing to the main article tells Google to focus SEO value there.
Fresh Challenges in 2025: AI and Syndicated Content
With the rise of AI-generated content, many sites now produce pages that look or read very similarly, even when they’re not exact copies. Google’s advanced AI can detect these “semantic duplicates.” If your site publishes multiple AI-written pages covering nearly the same topic, Google might treat them as duplicates. Canonical tags are more important than ever here — but they work best if paired with clear internal linking and strong content differentiation.
Another big shift: Google no longer recommends using canonical tags for syndicated content (like when your blog post appears on a partner’s site). Instead, Google suggests blocking those republished versions from being indexed with a noindex tag. Canonical tags across domains don’t always work the way people expect, so this change is huge for publishers.
How to Use Canonical Tags Correctly
Here are some golden rules for using canonical tags in 2025:
- Point to the main version – The canonical URL should be the page you want in search results.
- Use absolute URLs – Always use https://www.example.com/page instead of /page.
- Add self-referencing canonicals – Even your main page should include a canonical tag pointing to itself.
- Don’t canonicalise unique content – Use them only for similar or duplicate pages.
- Avoid chains or loops – Don’t point Page A to Page B and Page B to Page C. Keep it direct.
- Match signals consistently – Make sure sitemaps, internal links, and redirects all align with the canonical choice.
- Watch out for hreflang conflicts – Google clarified that canonical annotations with hreflang, lang, or media attributes may be ignored. Use proper alternate hreflang tags for international sites.
Common Mistakes with Canonical Tags
Mistakes can undo the benefits of canonicals. Some common errors include:
- Pointing canonicals to irrelevant or outdated pages
- Adding canonicals to noindex pages (Google may ignore them)
- Forgetting to update canonicals when content changes
- Misusing canonicals for paginated content (instead, use rel=prev and rel=next or let Google crawl naturally)
Example:
If /shoes/running has a canonical pointing to /shoes/old-running, you could lose traffic because Google will rank the old page instead of the new one.
Canonical Tags vs. 301 Redirects
It’s easy to confuse canonicals with 301 redirects:
- Canonical tag – Suggests the preferred version to Google, but duplicates remain accessible to users.
- 301 redirect – Forces users and search engines to the main version, permanently.
Think of a canonical as a recommendation and a redirect as a command.
Use canonical tags when you want duplicates accessible (e.g., for tracking or sorting). Use 301s when the old page should no longer exist.
Conclusion
A canonical tag may appear as a small piece of code, but in SEO, it plays a huge role. In 2025, using canonical tags correctly means not just preventing duplicate content but also aligning with Google’s broader signals and updated rules. With AI-generated pages, syndicated content, and 40+ signals in play, it’s more important than ever to be deliberate about which pages you want Google to rank. When done correctly, canonical tags will keep your site clean, focused, and competitive in search results.
Proper canonical tag implementation is key to stronger rankings. Our team can help you simplify the process and optimise your site for search engines. Connect with us to get started.