Canonical Tags: Fixing Duplicate Content Issues for Better SEO
Duplicate content is a bigger problem than you think. It confuses search engines and may lead to indexing issues, causing your pages to lose valuable visibility. Canonical tags are a simple yet effective solution to control duplicate content.
What Are Canonical Tags?
A canonical tag (<link rel="canonical" href="URL">)tells search engines which version of a webpage is the ‘master’ or preferred version. It prevents duplicate content issues when similar or identical content appears under different URLs.
For Example
Imagine you own a dental clinic called thesmileinsider.com, and you’re promoting a Free Dental Checkup for New Patients. To reach different audiences, you create two different pages:
- https://thesmileinsider.com/new-patient-free-checkup/ — Promoted through local search ads and community partnerships.
- https://thesmileinsider.com/first-visit-free-checkup/ — Shared on your social media platforms and email campaigns.
Both URLs lead to pages offering the same information. Without proper canonical tags, search engines may treat them as duplicate content, causing indexing problems or splitting their ranking potential.
Both URLs promote the same teeth-whitening offer. However, if both pages have identical content, Google may consider them duplicates, which could negatively impact your SEO.
How to Fix Using Canonical Tags
If you prefer to have /teeth-whitening-discount/ indexed as the main page, here’s how to apply canonical tags:
- On /teeth-whitening-discount/
<link rel="canonical" href="https://thesmileinsider.com/offers/teeth-whitening-discount/">- On /teeth-whitening-special/
<link rel="canonical" href="https://thesmileinsider.com/offers/teeth-whitening-discount/">This setup tells search engines to prioritize the primary offer page while avoiding duplicate content issues.
How to Check If Canonical Tags Are Working
To ensure proper implementation:
- Use Google Search Console: Inspect each URL to see the ‘Canonical’ section.
- Check the Source Code: Right-click on the page → View Source → Search for
><link rel="canonical">. - Use Online Tools: Tools like Screaming Frog or Ahrefs can quickly audit canonical tags.
When to Use Canonical Tags
- Duplicate content across multiple URLs
- Dynamic URLs with parameters
- Syndicated content on other sites
- Similar content in multiple categories
Lesser-Known Facts About Canonical Tags
1. Canonical Tags Are Suggestions, Not Commands
For search engines, canonical tags are signals rather than precise instructions. If Google comes upon another more relevant URL, it could ignore the canonical tag.
Example:
If you set:
<link rel=”canonical” href=”https://thesmileinsider.com/dental-implants-guide/”>
but most backlinks point to a similar page, Google may still rank the other page instead.
2. Self-Referencing Canonical Tags Are Recommended
Even if your website contains no duplicate pages, a self-referencing canonical tag helps prevent future SEO issues.
Example:
For https://thesmileinsider.com/teeth-whitening/, the page should contain:
<link rel=”canonical” href=”https://thesmileinsider.com/teeth-whitening/”>
This avoids accidental duplicate URLs from tracking parameters like ?utm_source=newsletter.
3. They Can Be Used Across Domains
Canonical tags allow you to show search engines which domain contains original content.
Example:
If a dental blog republishes your article, they can add:
<link rel=”canonical” href=”https://thesmileinsider.com/best-dental-tips/”>
This tells Google to rank your original post highest among others.
4. They Don’t Work for Different Language Versions
Canonical tags are useless in separating English from French versions of the same page. Instead, use hreflang tags.
Incorrect Example:
<link rel=”canonical” href=”https://thesmileinsider.com/dental-care-guide-en/”>
Correct Approach:
<link rel=”alternate” hreflang=”fr” href=”https://thesmileinsider.com/dental-care-guide-fr/”>
5. Canonical Tags Don’t Prevent Indexing
Use noindex instead of a canonical tag if you wish Google to delete a page from the search results.
Incorrect Way:
<link rel=”canonical” href=”https://thesmileinsider.com/main-service-page/”>
Correct Way to Prevent Indexing:
<meta name=”robots” content=”noindex”>
6. Wrong Implementation = Deindexing
Pointing canonical tags to broken pages might lead Google to deindex helpful content.
Example of a Mistake:
<link rel=”canonical” href=”https://thesmileinsider.com/deleted-page/”>
Fix: Make sure the canonical URL exists and isn’t redirected.
7. Duplicate Pages with Different Canonicals Confuse Search Engines
If two identical pages each claim to be canonical, search engines could overlook both.
- Conflicting Canonicals:
- Page 1: <link rel=”canonical” href=”https://thesmileinsider.com/service-a/”>
- Page 2: <link rel=”canonical” href=”https://thesmileinsider.com/service-b/”>
- Use Clear URLs: Each page should have a unique URL, like “example.com/products?page=2”, so search engines can find and index them.
- Avoid # in URLs: Search engines may ignore URLs like “example.com/products#page2”, which can cause indexing issues.
Fix: Both should point to one preferred page.
8. They Can Be Overridden by Redirects or Internal Links
Google might overlook your canonical tag if internal links redirect to point to another page while your tag points to one.
Example:
Canonical tag: <link rel=”canonical” href=”https://thesmileinsider.com/dental-plans/”>
But internal links point to /affordable-dental-plans/, causing Google to prefer the linked page.
Fix: Keep canonical tags, internal links, and redirects consistent.
9. Google Doesn’t Always Respect Canonical Tags on PDFs
If you try to set a webpage canonical to a PDF, Google may treat them separately.
Example: <link rel=”canonical” href=”https://thesmileinsider.com/dental-guide.pdf”>
The Right Way: Use structured data or link to the PDF from the main page instead.
10. Canonical Tags Work with Pagination, But Not Perfectly
When you have a long list of items on your website—like products or articles—you might split them across multiple pages for easier navigation. This is called pagination, resulting in a series of pages such as Page 1, Page 2, Page 3, and so on.
If paginated pages all canonicalize to Page 1, deeper pages may not be indexed properly.
Incorrect Example:
Page 2, Page 3, and Page 4 canonicalize to Page 1:
<link rel=”canonical” href=”https://thesmileinsider.com/blog/”>
The Correct Way: Use rel="next" and rel="prev" instead of a single canonical tag.
Conclusion
Using canonical tags can strengthen your site’s visibility and avoid potential SEO pitfalls. If you need help optimizing your dental website, contact we are here for expert SEO solutions!
