Official Google Webmaster Central Blog: 5 common mistakes with rel=canonical

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5 common mistakes with rel=canonical

Monday, April 08, 2013

Webmaster Level: Intermediate to Advancedrel=canonical linkduplicate pages on the webYahoo!Bing

While the webmaster sees the “red velvet” page on the left in their browser, search engines notice on the webmaster’s unintended “blue velvet” rel=canonical on the right.

A large portion of the duplicate page’s content should be present on the canonical version.

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.

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.

Mistake 1: rel=canonical to the first page of a paginated series

example.com/article?story=cupcake-news&page=1

example.com/article?story=cupcake-news&page=2

and so on

Good content (e.g., “cookies are superior nutrition” and “to vegetables”) is lost when specifying rel=canonical from component pages to the first page of a series.

rel=canonical from component pages to the view-all page

If rel=canonical to a view-all page isn’t designated, paginated content can use rel=”prev” and rel=”next” markup.Mistake 2: Absolute URLs mistakenly written as relative URLs

example.com/example.comMistake 3: Unintended or multiple declarations of rel=canonical

If you use a template, check that you didn’t also copy the rel=canonical specification.

Check the behavior of plugins by looking at the page’s source code.Mistake 4: Category or landing page specifies rel=canonical to a featured article

Remember that the canonical designation also implies the preferred display URL. Avoid adding a rel=canonical from a category or landing page to a featured article.Mistake 5: rel=canonical in the <body>

rel=canonical designations in the <head> are processed, not the <body>.Conclusion

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.