Google and the Canonical Link Rel

By  on  

Google has introduced a link tag rel value of canonical which is used for defining the value of the page that Google should use. Why? Lets say you have an eCommerce site and one of the product URLs is:

http://yoursite.com/product.php?p=david+walsh+blog+book

Imagine now that you can make a slight customization to the product that changes the URL to:

http://yoursite.com/product.php?p=david+walsh+blog+book&color=red

Uh oh -- Google sees duplicate content! The code shows essentially the same page so Google thinks you're pulling gangsta stuff. Now you can tell Google what URL to use for the current page to avoid duplicate content penalization.

The XHTML

<link rel="canonical" href="http://yoursite.com/product.php?p=david+walsh+blog+book" />

Don't let your website get penalized by Google; use this link/rel tag combination for your highly variable pages.

Recent Features

  • By
    39 Shirts &#8211; Leaving Mozilla

    In 2001 I had just graduated from a small town high school and headed off to a small town college. I found myself in the quaint computer lab where the substandard computers featured two browsers: Internet Explorer and Mozilla. It was this lab where I fell...

  • By
    CSS 3D Folding Animation

    Google Plus provides loads of inspiration for front-end developers, especially when it comes to the CSS and JavaScript wonders they create. Last year I duplicated their incredible PhotoStack effect with both MooTools and pure CSS; this time I'm going to duplicate...

Incredible Demos

  • By
    Comment Preview Using MooTools

    Comment previewing is an awesome addition to any blog. I've seen really simple comment previewing and some really complex comment previewing. The following is a tutorial on creating very basic comment previewing using MooTools. The XHTML You can set up your XHTML any way you'd like.

  • By
    Dynamic Waveform Visualizations with wavesurfer.js

    Waveform images are an awesome addition to boring audio widgets.  They can be functional as well as aesthetically pleasing, allowing users to navigate audio visually.  I recently found wavesurfer.js, an amazing waveform image utility that uses to Web Audio API to create super customizable...

Discussion

  1. Note that the All-in-one SEO WP plugin does this for you. Good to know should you bloggers be worried.

  2. I think the article could have given a bit more info on canonical urls…

  3. @Adriaan: Thank you for your comment. I could have but my fear is spending a ton of time on an explanation when 99% of people would prefer a brief explanation with a sample problem and solution like I provided. I appreciate your honesty!

  4. OK, I had to go to Google to find out where in the document this LINK goes… But this is good info, thanks for the the tip. Google implies that some other search engines look at this too.

  5. emceha

    time to google for more about canonical ;)

  6. Cool information!
    Liked the posts about firefox extensions too, really useful for beginners on that world.

    ps: you forgot to close the link tag.

  7. Add this code to the section of the page.

    < head >
    < title > Davidd Walsh Blog Book< /title >
    < link rel=”canonical” href=”http://yoursite.com/product.php?p=david+walsh+blog+book” />
    < /head >

    @Fabio, No missing < /a > tag as its a < link .. >

  8. Good I want to implement it first and have post this tips. Thanks

  9. great post is there any problem if i use rel tag for all of my links

  10. David,
    Thanks for the tip about rel canonical.

    Peter

  11. You can find more info here: http://support.google.com/webmasters/bin/answer.py?hl=en&answer=139394
    Thanks for the article.

Wrap your code in <pre class="{language}"></pre> tags, link to a GitHub gist, JSFiddle fiddle, or CodePen pen to embed!