by Scott Allen - March 9, 2009
Filed Under SEO
As you know, duplicate content can often create problems for SEO and hinder a website’s rankings. This particular problem shows up in a multitude of situations, including any time multiple URL’s are generated (tracking campaigns, etc), or where content is database-driven (for example CMS’s such as e-commerce or blogs).
It is always recommended that you keep your site’s URL structure as clean as possible, but recently the search engines have come together to create a backup option that can also help – the canonical tag.
To use it, insert the following in between the
</head> tags on your site.
<link rel="canonical" href="http://www.yoursite.com/page.php" />
- Only use the tag on pages within a single website (subdomains count).
- Relative or absolute links are fine, but the search engines recommend that you use absolute links.
Concerning the passing of link value, this tag will function similarly to a 301 redirect. All the pages that tag a certain URL as the canonical URL, will redirect the link juice to the canonical URL.
- Incoming links to all URLs will be consolidated to the one specified in canonical tag.
- Search engines will consider this canonical URL a “strong hint” as to the main page to index.
If you are using WordPress, you can easily implement this fix with Joost de Valk’s Canonical URL’s plugin.
More Info on Canonical Tags
- Canonical URL Tag – The Most Important Advancement in SEO Practices Since Sitemaps | SEOmoz
- Specify Your Canonical | Google Webmaster Central Blog
- Having A Crawlable Site Architecture Still Matters | Search Engine Land
You may also want to read: Duplicate Content Prevention: WWW vs. Non-WWW and .Htaccess
The All in One SEO Pack plugin now includes the same functionality as the Canonical URL plugin.