Posted: 08 Apr 2013 03:09 PM PDT
Webmaster Level: Intermediate to Advanced Including a rel=canonical link in your webpage is a strong hint to search engines your 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.
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.We recommend the following best practices for using rel=canonical:
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.
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.In cases of paginated content, we recommend either a rel=canonical from component pages to a single-page version of the article, or to use rel="prev" and rel="next" pagination markup.
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
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> The rel=canonical link tag should only appear in the <head> of an HTML document. Additionally, to avoid HTML parsing issues, it's good to include the rel=canonical as early as possible in the <head>. When we encounter a rel=canonical designation in the <body>, it's disregarded. This is an easy mistake to correct. Simply double-check that your rel=canonical links are always in the <head> of your page, and as early as possible if you can.
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