As my catastrophic canonicalization experiment and follow-up experiments showed, Google does honor rel=canonical even on very different pages, in some cases. Generally speaking, I think it’s best to reserve rel=canonical for duplicates or very-near duplicates.For example, if a product pages spins off into five URLs for five different colors, and each color's page only differs by a sentence or two (or an image), then yes, I think it’s fine to rel=canonical to the “parent” product page.Early on, there were hints that both Google and Bing preferred that you not overuse rel=canonical.Over time, though, their stances seemed to soften, and I’ve seen no evidence in recent history of a properly used, self-referencing canonical causing any harm.I’m not going to repeat all of Google’s answers, but this one is so frequently asked that it deserves more detail.Let’s say you have a series of paginated search results (1, 2, 3… These can be considered “thin”, from a search standpoint, so should you rel=canonical page n back to page 1?
Pagination for SEO is a very tricky subject, and I recommend you check out these two resources: Yes – in late 2009, Google announced support for cross-domain use of rel=canonical.
The subject of duplicate content is complex, and I’ve addressed it previously in detail.
For this post, I’m going to skip ahead and assume that you have a working knowledge of technical SEO and have attempted to use rel=canonical on your site.
It’s been over four years (February 2009) since Google and Yahoo announced support for the rel=canonical tag, and yet this single line of HTML is still causing a lot of confusion for SEOs and webmasters.
Recently, Google posted 5 common mistakes with rel=canonical – it’s a good post and a welcome bit of transparency, but it doesn’t address a lot of the questions we see daily here in Q&A.