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What a Canonical Link is and How to Use it Properly

on Web Design

Search engine optimization continues to be one of the most important areas of opportunity for many websites. Adhering to the strict rules set out by major search engines, especially Google, it is the best way to ensure that a website is placed on the first page of a keyword-targeted search and not on the last page of those results. Especially in recent years, as Google and other search engines have partnered to create SEO standards, this has become true for major corporate websites and small blogs alike. Whether it’s the eliminate of backlinks, the detection of keyword spam, or the implementation of the canonical link structure, a number of new tools are being used to help web developers leap to the front pages of any Google, Yahoo!, or Bing search.

The most recent development is the implementation of canonical links, which stretches back only to 2009. It was during the middle of that year when Microsoft, Yahoo!, and Google, all agreed upon the standard and its implementation in existing websites. The new link structure was developed as a meta tag, as opposed to a standard tag in the body of the page, and served to unify a website’s identical or similar pages into one “canon” or similar block of aesthetics and content. In the ensuing three years, some serious confusion has raised as just how this canonical link structure is implemented into websites, and where it’s appropriate for inclusion. Especially because it’s a meta tag, many developers have steered clear of canonical usage in their designs. Furthermore, the function of this tag can easily be confused with a 301 Redirect via an “.htaccess” file, making its inclusion even more confusing and often avoided.

The Canonical Link: What it Does for Search Engine Optimization

Modern content management systems have a really unique way of presenting content that allows it to be displayed in multiple places throughout the website’s URL construction. That’s because content management software typically places it into both a relevant category and into a date-based archive that can be perused by users at any time. Additionally, it will often place the entry on the homepage until it has been replaced by several newer composures. In all, when categories, tags, and date-based archives are combined, it’s possible for a single entry to appear up to four times within the same website, at the same domain name.

As far as search engines are concerned, every single one of these instances needs to be indexed separately and returned in search results as a completely separate entity. That behavior has not changed, even with the introduction of canonical links and the recognition of content management software as the primary driver of online content. So, without any further direction, search engines like Google, Yahoo!, and Bing, will just index a blog post four times and display it in search results four times. This is often why major search engines note that they “omitted duplicate results,” even when website owners know that their entry appears nowhere else but on their own website.

When a canonical link meta tag is included into a template, it essentially informs the major search engines that an entry page is part of a larger grouping of posts that should not be displayed in a duplicate manner within search results. For example, the tag could be displayed on every category and tag-based page that simply tells the search engine to consider those pages the same as a standalone entry page. It would then link together the standalone entry page, the category page, and the tag page, so that they are all perceived to be the same thing for the search engine. This boosts a website’s search engine optimization because the major search engines no longer consider every separate entry page to be a separate search result. They now view that content as a single, unified source, and they’ll rank it higher because it’s less “diluted” in search engine results. That can only lead to good things for the website’s administrator, as higher search engine rankings typically lead to more ad clicks, conversions, and e-commerce.

How a Canonical Link Meta Tag Differs from a Standard 301 Redirect

Anyone reading this entry and relating page locations to search engine optimization technique is probably thinking that a canonical link is just a less-invasive 301 redirection. That is actually not true at all, as a canonical link actually requires no action on the part of site users or the search engines. Indeed, Google themselves have noted that the canonical link is an “instruction that they’ll follow strongly,” rather than a requirement that they’ll be forced to adhere to.

A 301 Redirect essentially requires users, browsers, and search engine robots, to update their bookmarks to the new site of a website’s old content. This is typically done when a website switches domain names, changes its permalink structure, or commits some other major shift in both the “how” and “where” of its own legacy content. This is simply not the function of a canonical link. Indeed, the link itself does not redirect a user, browser, or search engine robot, to any of the site’s content.

Essentially, a canonical link sits within the page’s <head> tag and merely acts as an instruction to indicate which part of the website serves as the current content’s “parent” page. If the content belongs chiefly to a date-based archive, this will be indicated even on category and taxonomy pages. The search engine will then recognize that the archive page is the primary place where the content should be read, indexed, and interacted with, and it will update its own search results to reflect this.

But nothing will force the search engine to do this, and no forced redirection will happen if a user visits an entry’s category-based page from a search engine. They’ll still see that content, and the URL will still state that they’re on a category page — because they are. The tag simply has more to do with search engine semantics than it does with the physical location of the content itself, and that’s why it’s a valid and important part of search engine optimization for websites running on content management software solutions.

How to Employ the Canonical Link to Reduce Duplicate Search Indexes

The important thing to know about a canonical link tag is that it should never link to another version of the current post. This can create all kinds of problems with search engines, and they won’t know how to tell which content should be indexed and which content should be left alone. Instead, canonical links are used to link back to the “parent” page of a duplicate entry, and tell the search engine, essentially, “this entry is part of a category page” rather than “this content stands alone.” Here’s a common example:

The categorized entry is featured here:


The canonical link to reduce the duplicate entry would look like this:

<link rel="canonical" href="http://www.example.com/category/cookies/" />

This is pretty easy to do with permalinked URLs, but the same thing can also be accomplished when using a canonical link with standard URLs generated by a content management system. In that case, the root part of the URL becomes the canonical link. A typical example looks like the following:

The standard entry URL is here:


When altered by a canonical URL tag, this gets changed to the following example:

<link rel="canonical" href="http://example.com/blog?c=124" />

At all times, the entry’s own permalink or URL ID number should be removed from the URL and it should be linked back to the page which its own “parent.” This parent-child relationship is what search engines will interpret when crawling the website and they’ll be much more able to properly list and rank the website’s posts in search engine results.

Canonical Support in Content Management Systems: Things to Know and Quirks to Recognize

Widespread search engine support for canonical links has been around for roughly three years, but many search engines do not currently support this essential meta tag with their native feature set. That’s a major problem for websites that require this tag as the last piece of their SEO puzzle. The good news, however, is that the WordPress content management system has supported the use of canonical link meta tags since the release of version 2.9 of its popular software. These tags are automatically generated on non-index pages that are produced and rendered by the WordPress Dashboard and the database, and they can be really helpful when improving a website’s ranking in search results.

This comes with a major asterisk, however, as a number of high-powered WordPress developers have noted that the implementation of these canonical links is not as good as it should be, and in some cases the links are entirely wrong. Those things can actually negatively affect a website’s search engine rankings and overall search engine optimization, and that can be a real problem for users of the software who don’t modify the links to be a bit more appropriate. Because of this, WordPress developers have actually taken the remarkable step of creating plugins to specifically remove the software’s default canonical links from the header of every page.

Instead, those same developers are now releasing their own plugins that include much more appropriate canonical link meta tags in order to improve a website’s search engine optimization without the botched implementation pushed by default WordPress installations. In many of these plugs, a custom settings panel is created within the WordPress Dashboard that allows website administrators to define their own canonical links, which will override both the default WordPress setting and the plugin’s own default values.

Outside of the WordPress ecosystem, canonical links have largely failed to be embraced as a default setting in major competing content management platforms. MovableType, Joomla, and Drupal, all can support canonical links via a plugin. They do not, however, force canonical links on their users as an out-of-the-box solution. And, given the botched WordPress implementation of these links, that actually might be a good thing for many users.

The important thing to know when choosing a canonical link solution for any major content management platform is to understand that these links are a bit subjective and a bit complex to implement properly. They have been documented relatively poorly, especially by Google, and most developers are still learning how to use them properly in a way that does not damage their own search engine optimization. WordPress’ own developers adhere to an outdated and outmoded implementation of these links that has been proven to have negative effects, while other content management systems have taken a hands-off approach that allows their users to define their own uses for the links.

When in Doubt, Leave it Out

Canonical links are an important and sometimes essential tool when fully optimizing a website for great search engine rankings. However, they are not the primary way that Google ranks and rewards a website for relevant content in a keyword-targeted search. If anything, these links should be considered the icing on an already-robust search engine optimization cake. They might be the difference between landing on the first and second pages in some cases, but they won’t make a difference between a website being on page one, or page twenty.

The key to leveraging these links is to place them on the right pages, but not on all pages as in WordPress. Duplicate entries should be indicated by these links, and they should simply be shown to Google as the “child” pages of a category or tag, rather than as the primary source of content within the website. When that is done properly, canonical links can actually have a great effect on search engine rankings and move the site up a few notches in relevant searches.

Always implement these tags with care and, as always, be sure to use Google’s own tools to monitor how a website is performing after canonical link meta tags have been implemented. If adverse rankings follow implementation, it’s a good indication that the tags are pointing to the wrong content or parent page, and Google is pushing the website down accordingly.

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