Monday, April 08, 2013 at 3:09 PMWebmaster Level: Intermediate to Advanced Including a rel=canonical link in your webpage is a strong hint to search engines your about preferred version to index among duplicate pages on the web. It’s supported by several search engines, including Yahoo!, Bing, and Google. The rel=canonical link consolidates indexing properties from the duplicates, like their inbound links, as well as specifies which URL you’d like displayed in search results. However, rel=canonical can be a bit tricky because it’s not very obvious when there’s a misconfiguration.
- A large portion of the duplicate page’s content should be present on the canonical version.
- Double-check that your rel=canonical target exists (it’s not an error or “soft 404”)
- Verify the rel=canonical target doesn’t contain a noindex robots meta tag
- Make sure you’d prefer the rel=canonical URL to be displayed in search results (rather than the duplicate URL)
- Include the rel=canonical link in either the <head> of the page or the HTTP header
- Specify no more than one rel=canonical for a page. When more than one is specified, all rel=canonicals will be ignored.
One test is to imagine you don’t understand the language of the content—if you placed the duplicate side-by-side with the canonical, does a very large percentage of the words of the duplicate page appear on the canonical page? If you need to speak the language to understand that the pages are similar; for example, if they’re only topically similar but not extremely close in exact words, the canonical designation might be disregarded by search engines.
- and so on
- Verify that most of the main text content of a duplicate page also appears in the canonical page.
- Check that rel=canonical is only specified once (if at all) and in the <head> of the page.
- Check that rel=canonical points to an existent URL with good content (i.e., not a 404, or worse, a soft 404).
- Avoid specifying rel=canonical from landing or category pages to featured articles as that will make the featured article the preferred URL in search results.