This is a computer science term for standardizing data that has more than one representation. As it relates to SEO, canonicalizing URLs refers to consolidating the paths by which content on the web is accessed.
For example content on a website could be accessed at http://www.example.com as well as https://www.example.com. Even though people see the same website, search engines consider these two distinct URLs.
Basically canonicalization is a way to tell search engines which URL should be indexed in search.
Canonicalization is an important element to have configured on a website but is often overlooked. Canonicalizing pages provides a variety of benefits for a website when it comes to content and people being able to find it in search as well as ranking well in SERPs.
There are also a variety of ways to accomplish it without a lot of headache.
Canonicalizing pages helps lawyers avoid duplicating content on their website. It instructs search engines which page is the one that should be indexed and shown to users. There are a lot of articles on the internet about the dangers of duplicate content.
While there is no ‘duplicate content penalty’ from Google, it can be a negative on a website.
If you are having a website built or building your own, it may seem logical enough that there will not be two versions of the same exact page. In fact, it is unavoidable in many circumstances and you may not even know about it.
The following is a list of when it is ok to have duplicate content on a website:
• Printer-friendly versions of pages
• Mobile versions of pages
• Content that is a part of page architecture and similar across an entire site
Some e-commerce platforms and CMSs actually generate duplicate pages without lawyers ever seeing these extra copies. WordPress for instance has category and tag pages that have the same content as post pages.
For the most part it is ok to be doing this as long as you canonicalize your pages. As a best practice lawyers should also hide category and tag pages from search spiders.
There are a number of ways to canonicalize URLs1 depending on your level of expertise with coding and your current setup (which we will get to in a moment). First let’s discuss why canonicalization is even necessary.
Consolidation of Link Signals: A major underlying goal of Google and other search engines is to organize information on the internet for easy retrieval of content and attribution of link signals.
That task becomes much more complicated for search engines when the same resource is available in multiple locations.
For instance content that can be found at http, https, www.example.com, example.com, example.com/printer-friendly-version, and m.example.com; can be incredibly difficult to assign the weight of a backlink to.
Tracking: Measuring visits to a page can get confusing when there are multiple versions of it. For example you might see x-number of visits to a blog post on one domain but that may not be the true metric since you do not have reporting on visits to another domain with the same content.
One potential scenario could be visits to a desktop and mobile version of a page.
Syndication of content: If you syndicate content through an RSS feed on the internet, setting a preferred URL via canonicalization is a good idea. That way any links created through the syndication process will be consolidated with that URL.
Setting a Preferred URL
You can let Google and other search engines know that a page they are crawling is the preferred one to index. You can do this by adding a canonical tag in the header of the page. Here is a rel canonical example:
<link rel=”canonical” href=”www.preferredURL.com”/>
This method works best for more traditional websites built without using CMS. CMS’s often work by using one universal template across all pages that have the same code in many areas (one of them being the head section where this tag would normally be placed).
If you have multiple versions of a page and for whatever reason cannot eliminate duplicate versions or specify a preferred URL, you can redirect duplicate pages to the one you want indexed in search.
You would use the code 3012 to indicate to Google that these redirects are permanent and the page being redirected should no longer be included in the index.
Redirects can be implemented in a variety of ways either with your hosting account, through server configuration files like .htaccess or web.config, or through meta tags (which is not ideal).
The reason meta tag redirects are not ideal is because they create a poor user experience.
Use a Sitemap
You can indicate in your website’s site map3 which URLs are the canonical versions of pages. This process is a bit more tedious because then you have to go through your sitemap manually (when they are typically generated automatically) and specify your preferred URL.
You would then have to submit your site to Google Webmaster tools in order to submit your sitemap and preferred URLs.
The easiest way for lawyers to implement canonicalization on their site is to use a WordPress plugin. If you don’t have a WordPress site, there is a great tutorial here4 on setting up canonicalization for a traditional website.
For All-in-One SEO, simply click on the plugin’s configuration page and then make sure the canonical URLs check box is checked.
In Yoast URLs are canonicalized site-wide when the plugin is installed and configured however you can change the canonical URL on a post by post or page by page basis. Right in the page or post editor, click the advanced icon on the Yoast SEO settings and change the canonical URL if desired.