URL Canonicalization: The Missing Manual. (form SEO book), Canonicalization can be a confusing area for webmasters, so let's take a look at what it is, and ways to avoid it causing problems. How Can I Tell If Canonicalization Issues Are Affecting My Site? Besides working through the checklist performing a manual check, you can also use Google's cache date.
Matt Cutts SEO Advice: url canonicalization A talk a little bit about canonicalization, www vs. non-www, redirects, duplicate urls, 302 “hijacking,” etc. so that we’re all on the same page.
Q: What is a canonical url? Do you have to use such a weird word, anyway?
A: Sorry that it’s a strange word; that’s what we call it around Google. Canonicalization is the process of picking the best url when there are several choices, and it usually refers to home pages. For example, most people would consider these the same urls:
www.example.com
example.com/
www.example.com/index.html
example.com/home.asp
But technically all of these urls are different. A web server could return completely different content for all the urls above. When Google “canonicalizes” a url, we try to pick the url that seems like the best representative from that set.
Google webMaster Tools about Canonicalization Many sites make the same content available via different URLs. Say you have a clothing site and one of your top items is a green dress. The product page for the dress may be accessible through several different URLs, especially if you use session IDs or other parameters:
To gain more control over how your URLs appear in search results, and to consolidate properties, such as link popularity, we recommend that you pick a canonical (preferred) URL as the preferred version of the page. You can indicate your preference to Google in a number of ways. We recommend them all, though none of them is required (if you don't indicate a canonical URL, we'll identify what we think is the best version).
This includes tips on:-
Set your preferred domain
Specify the canonical link for each version of a page
Indicate your canonical (preferred) URLs by including them in a Sitemap
Indicate how you would like Google to handle dynamic parameters
For example. Set your preferred domain :-
Setting your preferred domain tells Google which version of your site's URL (http://www.example.com or http://example.com) you prefer. Preferred domain (www or non-www). The preferred domain is the one that you would liked used to index your site's pages (sometimes this is referred to as the canonical domain). Links may point to your site using both the www and non-www versions of the URL (for instance, http://www.example.com and http://example.com). The preferred domain is the version that you want used for your site in the search results. If you see a message that your site is not indexed, it may be because it is indexed under a different domain. For example, if you receive a message that http://example.com is not indexed, make sure that you've also added http://www.example.com to your account (or vice versa), and check the data for that site.
If you set your preferred domain as http://example.com, we'll treat links to http://www.example.com exactly the same as links to your preferred domain.
To set the preferred domain for a site, click Site configuration, and then click Settings. In the Preferred domain section, pick the option you prefer.
Canonicalization Prevention Guide
Canonicalization, or more specifically the creation of duplicate content due to the way web server software handles variations on URLs, has become a much discussed topic here. Specific code snippets to resolve the problem in different situations have been widely discussed, but there is no single place that contains a list of different methods. I created this thread to list several of the more common ways of eliminating the two main types of canonicalization, www vs non-www duplication, and / vs /index.html canonicalization. All of the examples will handle subdomain issues (www vs non-www), directory root issues (/ vs /index.html) and secure server (http vs https) issues if possible.
Yay or nay: Putting a canonical tag on individual product review pages that each points to the 'all reviews for this product' page for the particular product.
Assuming we're not really that keen on the individual review pages ranking.
Advice The main idea of Canonicalization is to reduce try Duplicate Content. Using dynamic parameters e.g. '&value=132', '&query=this' could have an impact. This could also apply to redirects where ones web page redirects to another web page. Avoid Duplicate Content. Using SLL, Secure Socket Layer 'https' could also have an impact. The date and time of URL's and redirects could have an impact.
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