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Canonicalization in practice: which solution fits the needs?

Hi there!

From this day on you will find my weekly thoughts about online marketing here, blogging to you every monday. Before I continue, let’s first define “online marketing” – so you know what to expect from me, and I know what to expect from you in your innumerable comments you’re gonna post 😉 Online marketing in practice includes for me everything about SEO, linkbuilding, Google Analytics and Adwords but also digital newsletters, affiliate marketing or – more in general – online consumer behaviour. Let’s start off today with an important SEO item: Canonicalization (the word is more difficult to pronounce than the practical application of it.

In SEOmoz’ article about canonicalization ( it’ s clearly stated why this is important and how you implement it on your site. The main reasons to use canonicalization is to prevent duplicate multiple URLs for the same content (e.g. a webshop that shows a product on a sales promo page and completely the same info when one navigates to the product via the product category set), outside links to same content URLs or to guide the google bot in choosing the right URL you want in the SERP. The methods to do this is with 301 (permanent) redirects or a linktag using Rel. Canonical for the webpage.

What I would like to clarify in this post is the antecedent step: What does it mean in pratice and how you deal with the two different methods. In practice the www vs the non-www URL is the most well known example of using canonicalization. But logically this holds for all URLs that navigates to the same content pages, like:,, etc. From a usability point of view one may want all the URLs to be valid, redirecting to a single URL content page, which is the only one visible on the SERP’s.

But from a SEO point of view: which URL you find best? Which one do you want to be indexed by google? And will you choose the 301 redirect for it or a canonical URL? Suppose you want to use keywords in your URL, to create a Search Engine Frienly URL (SEF). The old URL is The SEF URL is When you use a 301 redirect you actually “tell” the Google bot the domain doesn’t exist anymore and it can be erased from indexing while on the same hand you “tell” the bot the opposite; the domain does exist but only with a keyword included. This will cause an infinite loop and will only be applicable when you decide to use a complete new domain for the content page.

An optimal solution in this situation is to use a canonical URL: will be the only one indexed by the search engine bot. The old URL ( might still be valid and visible in the browser when it is typed in directly, though it wont be visible anymore for the search-visitors. Further more, the new URL will optimal benefit from the PageRank and Linkjuice the old domain has generated during the time it was indexed.

Ofcourse, there are many distinct situations to use some way of redirecting URLs. Feel free to post your SEO cases and I would be pleased to discuss them with you.

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