Canonical tags essentially tell search engines that very similar or identical content exists on multiple URLs, and specifies the preferred URL for search engines.
This specification, introduced in April 2012, refers to an HTML link element. Use the attribute link rel=“canonical” (don’t forget to close the tag!) in the <head> element of a webpage that you want search engines to redirect to another. Doing so instructs search engines under which URL to index specific page content. This ensures that varying URLs offering similar or identical content are accounted for in the SEO realm.
Below are five different URLs that direct to the same homepage content for a website:
zurping.com
www.zurping.com
https://m.zurping.com
https://amp.zurping.com
https://zurping.com?ref=twitter
Search engines cannot know which page, although they all produce identical content, is the preferred URL. This is especially important to note for separate mobile and desktop versions of webpages. An engine might just select a canonical URL algorithmically, so it is beneficial to instruct the engine what to do in this case. We can’t let machines make all the decisions!
Using canonical URLs in SEO indicates the URL others will see in the search results. Both search engines and companies prefer a page be accessed via a clean, nice looking URL that may more specifically describe the content rather than a jumble of letters and numbers. Canonical URLs make that possible.
Tracking metrics is what SEO is all about, and canonical URLs make it easier to track a single product or topic (one URL for specific content).
Canonical URLs consolidate link signals for similar or identical pages so that all traffic is directed to an authoritative URL. This is huge for syndicated content published on other domains, and more specifically called the cross domain rel=“canonical”. Page ranking credit can be consolidated to your preferred URL. Duplicate content need not compete!
It is most often recommended that rel=”canonical” be used as the means of consolidating very similar or identical content for search engines, but there are three additional ways of canonicalization to keep in mind.
A 301 redirect (status code) creates a permanent redirect from one URL to another. This sends search engines and Internet browsers to a different URL than the one requested or selected from a search engine results page.
Once a website is verified, setting passive URL parameters in the Google Search Console indicates to Google that certain URL parameters should be ignored.
Finally, a location hash or fragment identifier (a URL with a # at the end of it that points to a specific section on the page) is considered by search engines to identify a single URL. Jumped content will be canonicalized to the same URL.
“If there are no technical reasons not to do a [301] redirect, you should always do a redirect. If you cannot redirect because that would break the user experience or be otherwise problematic, set a canonical URL.” – Joost de Valk, Yoast Founder & CEO
STOP!
Always use robots.txt to instruct Google which pages to disallow from a search. However, using robots.txt for very similar or identical contents crosses any ranking, engagement or content signals and generally hurts the webpage’s SEO value.
Neat freaks beware! Non-canonical versions cannot simply be deleted. That old post or product might be just begging to be removed from a page containing duplicate content, but doing so will screw up links referencing the content in other places. Only delete if a page was erroneously made or is very new and boasts almost no traffic.
SEO and canonicalization are no joke. To maximize the SEO value of content found on different URLs, use rel=”canonical”!
Here at LA SEO, we are familiar with working on sites anywhere from 25 pages to a million pages. Especially in e-commerce, canonical tags are essential. For example in e-commerce, product templates have specific canonical tag rules. Filters can create a mess of additional pages. E-commerce is more complex than informational sites and thus we can’t stress enough the importance of canonical tags.
Protip: Canonical tags are only one piece of the puzzle to fully optimizing your site. You want to control what URLs get built. When you get to adding attributes, it can get messy. You need to control how urls are built with priority ordering.
When the same product is in two collections generates two product urls but the true url doesn’t have collections in the url. Your Shopify site doesn’t link directly to the true URL. Don’t worry, we can fix this for you. We can get your system to try to link correctly to the canonical versions!