These URLs are all different:
Why is Canonicalisation important to SEO?
Canonicalisation problems are very important to SEO. When a single piece of content – a paragraph or page appears in multiple locations on a site or even on a different site, this causes major problems for search engines in that they aren’t sure which page they should be returning for a particular search. If you have duplicate content on the same site or the same content on a different site, this will be having a detrimental affect on your SEO and you should look to rectify this.
How to fix duplicate content issues
- Change your Content Management System (CMS) to generate only the URLs you want. “Normalise” URLs
- Pick one “canonical” URL and ensure you link consistently within your site
- Make all the non-canonical URLs do a permanent (301) HTTP redirect to the canonical/preferred URL
- Google’s Webmaster Tools: specify www vs. non-www
- Break ties in Google by submitting your preferred URL in a sitemaps file
Tough Duplicate Content Issues
- Sometimes can’t generate permanent/301 redirects
- Can’t help how people link to you
- Uppercase/lowercase paths
- Session IDs
- Tracking codes, analytics and landing pages
- Sorting by ascending vs. descending
- Breadcrumbs (the user’s previous web page)
Questions and Answers
Q: Does this work across domains?
A: No, only on the same domain
Q: Does this work across sub-domains/hosts?
A: Yes. So zeta.zappos.com could suggest www.zappos.com as a canonical URL
Q: Can I use this to suggest http://example.com be the canonical URL instead of https://example.com?
A: Yes, absolutely
Q: What’s the difference between this and a 301/permanent redirect?
A: They are very similar, but sometimes you don’t have the easy ability to generate 301/permanent HTTP redirects
Q: Do the pages have to be bit-for-bit identical?
A: No, but they should be similar. Slight differences are okay
Q: Can I use relative or absolute URLs?
A: Yes, but we highly suggest that you use absolute URLs. This is a powerful tool, and absolute urls leave less room for error
Q: Can you follow a chain of canonicals?
A: We may, but don’t count on it. Point directly to the final URL.
Q: What if I point to a 404? Or have an infinite loop? Or I point to an uncrawled URL? Or www/non-www conflict?
A: Search engines will handle it as best they can. Don’t cross the streams!