Google help SEO by extending support for the canonical tag

Google originally introduced the canonical tag to help resolve duplication issues on internal pages within sites. I often used it to resolve canonicalisation issues on sites such as duplicate home pages, where a 301 redirect could not be implemented.

It has proved very useful and now other major search engines also support the use of this canonical tag.
Google have now extended the support for this tag by allowing it to be used across two different domains.

Here’s a few issues that you need to keep in mind when using this tag across domains:

• The page on which you are using the canonical tag needs to contain similar content to that which you are pointing the canonical tag to.
• Do not noindex, nofollow the page containing the canonical tag, as this will prevent Google from crawling the page, and therefore prevent it from seeing the canonical tag.
• If you are offering some of your web content for syndication, you could come to an arrangement with your publisher whereby they include the canonical tag on content that is similar enough to warrant its use.
It is important to remember that if it is possible to 301 redirect a duplicate page then this should be put in place. The canonical tag is used as a hint only and it is not guaranteed that the search engine will take notice of it.