The What, Why, and How of Canonical Tags & URLs

“这是canon!"

You might've heard this phrase used to describe a creative piece that stays true to an original piece of work or fictional universe.

If you're familiar with canon, you are well on your way to understanding canonicalization and how it impacts web pages.

Here, let's explore what canonicalization is, why it matters for SEO, and how to add the tag to your own website.

What is canonicalization?

规范化声明了原始或首选的网页，该页面有助于整合重复页面以爬行。

没有命名规范的URL, web爬虫程序可以crawl and index multiple versions of your web page.Google indicatesthat it will crawl non-canonical pages less frequently to reduce the crawl load on your website.

Less frequent crawling of low-quality, duplicate pages means more important pages can be prioritized for crawling, instead.

Okay, but why would we purposely have duplicate content? Well … ever post your content on your website and also on Medium? Or, perhaps after guest posting you place a version of the blog post on your website, as well.

To do so, you should reference the original version as the canonical URL. Canonical URLs can reference different domains — meaning the canonical can be on another website.

即使您没有积极创建跨通道促销的重复页面，因此自然而然地发生了重复the different parts of a web address. Does your website use a secure protocol, like HTTPS? Then you may have an HTTP and HTTPS version of your webpage.

The same goes with www vs. non-www. Does your website use trailing slashes, or not? If your website doesn't always redirect to the preferred version of your page (secure or not, www or not, and trailing slash or not), duplication can occur.

Even if you are forcing the preferred version through a redirect, query parameters used for tracking visits or filtering views on a page can also look like separate URLs to crawlers. Declaring a canonical URL indicates to web crawlers to ignore query parameters or other versions of the URL.

What is a canonical URL?

The external resource element defines relationships between the current page and other resources. A "rel" attribute is used on the tag to indicate the type of relationship. Some common link types include "prev" and "next" for pagination, "stylesheet," and, of course, "canonical."

The tag uses thehrefattributeto set the URL that serves as the canonical to the active page. Although these are intended to be external resource links, the canonical URL can be "self-referring," meaning it is the exact version of the current page. Using self-referring canonicals helps to reduce the unnecessary crawling of non-preferred versions of your page, as long as you are always using the absolute URL as thehrefvalue.

In Google Search Console, you can use theInspect URL toolto understand what Google considers the canonical URL, even if you have not set one. Even when you have declared a canonical URL, Google will sometimes still pick a different URL, listed as the "Google-selected canonical." Because of that, canonicalization is not a guarantee that Google will select your preferred version or that other versions will not be indexed.

How to Add a Canonical Tag

Add a Canonical Tag in an HTML Document

As mentioned, you can use the element to set your canonical URL. Link elements are self-closing tags.The "rel" and "href" attributes are required.

要在元素中添加<链接>元素的HTML文档中的规范链接。确保“ rel”属性值设置为“规范”。请记住将您首选的网址的绝对URL作为值hrefattribute.

<头>

https://www.mypreferredwebaddress.com/canonical-url">

Add a Canonical Tag in HubSpot

In HubSpot, you can set your canonical URL in the individual page or post settings under Advanced Options.Read more about canonical URL settings options.

Add a Canonical Tag in WordPress

Common WordPress SEO plugins, including Yoast and RankMath, simplifies setting up canonical URLs, especially for several pages. If you are a little more advanced and don't want to add another plugin, it is possible to update the canonical URL using WordPress Hooks too.

1. Using the get_canonical_url Hook.

A filter WordPress hookallows you to modify data as WordPress is executing. The add_filter() function accepts at least two parameters, a tag and a callback function. The tag would be the hook, which in this case isget_canonical_url.

The callback function parameter would be the name of a function you create that returns the canonical URL. The callback function could use conditional statements to match to specific posts.Refer to this Stack Exchange answer example.

在示例中，“ WPSE_302620_CANONICAL_URL”回调函数使用IF语句来返回新的规范ID时，该邮政ID（作为该函数的参数传递）与特定帖子匹配。考虑到这一点，该解决方案似乎是一些帖子或帖子类型的修复程序，但可能无法很好地扩展。要应用几页，使用插件可能是最好的选择。

2. Using the Yoast Plugin.

If you are using Yoast, you can apply canonical URLs to posts, pages, and taxonomies. Select the type of content you want to edit from the left-hand menu, then "edit" the individual piece of content. In the Yoast SEO meta box, toggle the "Advanced" section. Add your preferred web address in the "Canonical URL" field and save.Learn more about Yoast's canonical URL settings.

3. Using the Rank Math Plugin.

While editing your specific page or post, select the "Advanced" tab on Rank Math. Add your preferred web address in the "Canonical URL" field and save.Learn more about setting canonical URLs in Rank Math.