Summary
If your website content is available on multiple domain names you may end up with duplicate listings. Duplicate content is bad for your website’s ranking as both your domain names compete for the same users, reducing their importance and rank.
One method of preventing duplicate content is to include the canonical link-tag inside your <head> tags. It allows you to publicly specify your preferred version of a URL. Search engines that support the link-tag will follow the link and treat the URL you specify as the main domain.
For example, including the below canonical link-tag inside the tags on both example.com and www.example.com would lead to just example.com being listed in Google.
<link rel="canonical" href="http://example.com/" />
Benefits
- Your users will see your preferred domain.
- Stops duplicate content.
- Optimizes your search listings.
- Increase your website’s search ranking.
- Enhances online branding.
- Gives you control over your listings
Support
Currently Google, Yahoo, Bing and Ask.com support the canonical link-tag.
Markup
Insert the following markup inside the <head>, changing example.com to your preferred domain name or URL
<link rel="canonical" href="http://example.com/" />
