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How do you solve a duplicate content problem? How does Google decide which version of a page to show in search results? Canonicalization!

Canonicalization is how you tell search engines what link is the “official version” of a page.


What is Canonicalization?

Canonicalization sounds very technical, but put simply its how you tell search engines what link is the “official version” of a page. Let’s say your website’s homepage can be reached the following several URLs:


Search engines split the incoming links across those URLs and divide their value across those variations. Using canonicalization, you can ensure that all the value from the duplicate URLs counts for one URL, which will contribute to a better position in search results.


How Do You Canonicalize a Page?

There are two recommended approaches to canonicalization: 301 Redirects and the Canonical directive. The approach you use depends on the kind of duplication issue you’re trying to solve.

The Rel=Canonical Directive

Generally, the Canonical directive is Google’s preferred approach. By declaring a Canonical URL for a page directly in the source code, it will always be present wherever that content is visible. Using this method, you don’t have to write lengthy lists of redirects for every possible URL or disrupt your visitors by moving them from one URL to another.

This method is especially useful for product pages that are found in multiple categories and sites with complex navigation structures. It’s also used for guest blog posts and syndicated content, to pass the value back to your original version.

301 Redirects

A 301 Redirect tells your browser to reload a page at a new URL. They are useful for cases where underlying technical issues create many possible URLs for a page, or if you have recently moved your site to a new domain. By redirecting visitors to the new location, you can ensure that visitors are always at the correct URL. However, 301 redirects don’t pass link value perfectly.

301 Redirects lose between 1 to 10 percent of link value (source: for the first redirect, and it goes up dramatically if you have multiple redirects in sequence.

When Not to Use Canonicalization

There are some cases where canonicalization isn’t the right method, and can actually be detrimental to SEO. The most common example is paginated content, that is, related content divided across several pages, such as a blog that has many pages of older articles. In this case, there are other directives that apply to related pages.

A Cautionary Note on Canonicalization

Canonicalization is a very powerful tool, and like many tools, they can be harmful if used improperly. Incorrect canonicalization can lead to huge SEO issues including removing pages, or even entire sites, from search engines’ results.

Some of the most common errors include:

  • Multiple canonical directives on a page can cause search engines to ignore all your directives, slowing down your SEO efforts.
  • Canonicalizing all your pages to one URL can incorrectly remove valid pages from search results. Correcting this can often take months, as pages are gradually re-indexed by search engines and have to build up position anew.
  • Dynamically generating Canonical directives is especially dangerous. It can have security implications and play havoc with SEO at the same time.

Used properly, Canonicalization is a tremendously useful, powerful tool for shaping link value and smoothly guiding visitors to your content. For expert advice tailored to your specific situation schedule a consultation with New Perspective.