Dealing with URL canonicalization issues

While not the most talked about SEO problem , URL canonicalization is certainly a very important one. Judging by the number of businesses not aware of it I thought a quick post could help clarify what it is and how to fix it.

What is a canonical page?

While I could try to explain what canonicalization is myself, I'll just quote Matt Cutts as he is the expert on all things SEO at Google:

 "A canonical page is the preferred version of a set of pages with highly similar content" 

In SEO terms, this means that a page or set of pages with similar content should only display under 1 URL.


Canonicalization issues and consequences

Problems arise when a specific page or very similar pages display for different URLs. If these pages are too similar to each other, search engines and particularly Google, may see them as duplicate content which could lead to penalties and a potential ban from the SERPs. For SME's this could mean loss of traffic, revenue and the end of the road in the worst cases.


Homepage canonicalization issues

The most common type of canonicalization issues I've come across are related to homepage URLs. A lot of websites' homepages will display for various URLs.
eg: www.website.com, website.com. www.website.com/home, website.com/home.....

While this may not seem like a major issue as visitors can still browse the website no matter what URL they use, it is a very serious SEO issue. Search engine spiders will crawl the site and potentially index 4 URLs with the same content, creating an obvious case of duplicate content as the page is always the same. This problem will also be reflected site wide as each individual page will be displaying for the www and non-www URL.

Canonicalization solutions

There are 2 common methods used to fix canonicalization issues: the use of rel="canonical" link in the code of the pages (in the head tag) and 301 redirects.

Both methods are fairly straightforward to implement and are very effective ways to avoid penalties for duplicate content.

• The canonical link

The rel="canonical" link will basically indicate to search engines that a specific URL should be indexed as the main one for similar pages.

This link needs to be added to the tag of the source code of the non-canonical pages in the following format (where the URL used is the one of the page you want to be indexed  - www.example.com in the link below):

• 301 redirects

301 redirects are a common search engine friendly method used to tell search engines that a page has permanently moved and should be redirected to another page. For homepage canonicalization issues, it means that a website will only display for www.website.com since the non-www or /index, /home versions will be automatically redirected to that URL.

As this is a slightly technical server side operation, I'd strongly advise to get the help of a web developer before implementing these redirects.

There are a lot of resources available online on how to fix canonicalization issues, and here are a few of the best ones:

- SEOMoz, canonicalization best practices
- Matt Cutts on canonical link tag
- Webmaster tools help on canonical links
- Webmaster tools help on 301 redirects

• Webmaster tools preferred domain

In addition to the 2 methods above,  if you have a Webmaster Tools account for your website you can also set your preferred domain there to ensure Google indexes the correct pages.

By following the steps above you should be able to avoid canonicalization issues and focus on other SEO aspects for your business. Remember that search engines look at hundreds of elements to index websites, and any improvements you make could bring great benefits to you and your business.

If you've faced or are facing canonicalization issues with your website, feel free to share your experience.