September 2, 2015

Canon Law: What Canonical Tags Can Do For Your Content

How do you make sure your Google juice is as strong as possible and the best of your content makes the strongest showing it can? There are a lot of answers to this question, but one of them is canonical tags. They’re not something all marketers have heard of, though. So what are they, how do they work and how do they make a difference?

When search engines find content that seems to appear in multiple locations, they can have a hard time deciding what to show in a results page. For example, what if the same content appears on and A human may understand that those are all the same page, but search engines may think they’re separate. This dilutes the authority of the URL, splitting it among three instead of concentrating it in one result.

This is where canonical tags come in.

A canonical tag is an HTML element that helps a webmaster tell a search engine which content they would prefer to be indexed and shown in search results. Canonical tags in the above example would designate which of the three pages to index. This ensures that the right content and the preferred URL show up, and it tells search engines which content to attribute trust, authority and other metrics that enhance ranking signals.

Canonical tags can be confused with redirects because both fix confusion caused by multiple versions of webpages. A redirect, though, pushes a search engine (or user) from one page to another by explaining that the old page no longer exists, whereas canonical tags don’t send users anywhere and aren’t used when old content is moved.

Here’s one example from the REMICADE® website. Because REMICADE has several indications, a support page under each indication section contains duplicate content, yet each has a different URL.

Another example is the MOTRIN® site. It has been built within both a secure and an unsecure server, so there are two versions of the site ( and The two versions would be indexed and viewed as different websites by search engines unless canonical tags are employed.

Several types of canonical tags can help in different situations:

  • Classic or “A-to-B” — These explain which piece of content is preferred, leading the search engine from the non-preferred “A” version to the preferred “B” version. This is often for print-only pages.
    • Duplicate content — If there’s a situation in which duplicate content is unavoidable, a classic canonical tag can help search engines go to the most important place.
    • Server issues — Sometimes a server creates situations where default pages are generate that duplicate the homepage. A classic canonical tag can tell a search engine which one to focus on.
  • Self-referencing or “A-to-A” — This explains the proper URL to use when a session ID or server issue creates multiple URLs.
    • UTM parameters — Tracking tags called UTM parameters help analytic software measure properly. They can confuse search engines, too, though. A self-referencing canonical tag can straighten this out.
    • Session IDs — Sometimes a unique ID is generated for each visit to a website, and this can show up as a new URL. A self-referencing canonical tag can explain that the main URL, without the session ID, is what should be indexed.
  • Mobile or alternate — This helps search engines to display the proper URL depending on whether a searcher is using a mobile or a desktop browser.
    • Mobile sites — While the best mobile experience is with a responsive design, in some cases, a site will have both a desktop and a mobile version. In these situations, a mobile or alternate canonical tag will help.

Of course, the best course of action is to avoid the need for canonical tags — e.g., removing duplicate content, building a responsive website and ensuring that you have the proper server settings in place. When a problem can’t be avoided, however, the right type of canonical tag can ensure that search engines properly index your site. People like our SEO and inbound marketing experts can give you guidance and support to make that happen.