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When Google announced support for the canonical tag just about a year ago, webmasters were excited for the possibilities of a serving a 301 redirect to spiders but not users. But when should you not use it?
A Google Webmaster Help thread has Google's JohnMu explaining some situations as to when you should or should not use it.
In summary, think of the canonical tag as a real 301 redirect for spiders. If a spider is redirected away from new content, then that is an issue. When it comes to paginating content, such as product category pages or article archives, you really need to give a way for search engines to find that content. If you set the canonical tag to redirect spiders from page 2, 3, 4, etc of your product category pages to page one, then the spiders might never be able to index the products on page 2, 3, and 4.
John explained this well, saying:
Pagination: this is complicated, I personally would be careful when using with rel=canonical with paginated lists. The important part is that we should be able to find all products listed, so at the very least those lists should provide a default sort order where we can access (and index) all pages. Since this is somewhat difficult unless you really, really know what you are doing, I would personally avoid adding rel=canonical for these pages. One possible solution could be to use JavaScript for paginated lists with different sort orders, for example, that way you would have a single URL which lists all products.
This is something to keep in mind when building out the canonical tag within your content management system.
Forum discussion at Google Webmaster Help.
Comments:
Andy
02/09/2010 02:37 pm
Has anyone ever used 'noindex,follow' for paginated pages before? Its worked quite well for me. I do not see the purpose of using a canonical tag in this instance.
Seo Fail
02/09/2010 08:00 pm
also use the method of meta noindex, follow to index products. But on large sites (thousands of offers), an important part of Googlebot can be used to crawl pages paging hollow. I think that advanced use of XML sitemap can help to list all product pages, working on the priority parameter. For example, placing a high priority to those most sold .... At each site the problem, I think there is any silver bullet, and that various actions on the nofollow,canonical tag, JS, be used depending on the site.
Jaan Kanellis
02/11/2010 05:40 pm
Why would you want those pages 2,3,4 indexed? Sure you want them crawled, but indexed and competing with page 1?
Clark
02/16/2010 06:19 pm
Jaan, You might want pages 2, 3, 4, etc indexed if the content on those pages are unique. This would help you appear in more long tail queries. For example, you sell thousands of types of Widgets and green, left-handed widgets are on page three, then you'd want that page indexed. Page 1 is probably going to be the most popular widgets (probably blue, right-handed widgets), but you don't want to forget about the long tail!
Jaan Kanellis
02/18/2010 02:33 pm
true but look at it from a forum perspective. all those pagination pages dont look unique at all.
Keith Edwards
09/23/2010 07:43 am
I was going to add a canonical and found this forum which is quite advanced for me. Could you use canonical for example my site http://www.eco-pressure-clean.co.uk to keep users to my www site as some type in the url without the www. ? Thanks Keith.