The Canonical Tag in SEO Explained: Avoiding Duplicate Content Penalties

Duplicate content may seem like a harmless oversight, for those who are less concerned with the nitty gritty of details that browsing users might consume – it has the capacity, however, to silently sabotage your website's performance. When search engines encounter multiple pages with similar content, they struggle to determine which page should rank – not to mention suspicions on generating satellite sites, for the purposes of expanding your net reach in an unethical way. Ultimately, this can lower your rankings, dilute your search visibility, and impact your overall credibility. Implementing the canonical tag in SEO, in this case, serves as a marker of sorts that aims to clarify what pages are original, and which can be neglected.

For Australian businesses heavily invested in digital marketing, this can quickly become a significant and burdensome issue – but it doesn't need to be.

Canonical link tags, when used effectively, offer a straightforward and effective solution as they help search engines identify the right pages to rank and index. Learn more about this strategy, with our team at SEO Sydney below!

What Is a Canonical Link Tag, and Why Does It Matter?

A canonical link tag is an HTML snippet that tells search engines which page is the original, in a set of duplicate or near-duplicate pages on your site. This allows platforms like Google to determine which to index as the genuine article, show in search results, and consolidate link equity.

Here is an example of a canonical tag:

<link rel="canonical" href="https://example.com/" />

Why Use Canonical Link Tags?

Canonical link tags are key to solving issues with duplicate content. While this problem isn't always malicious, it can present a set of problems for search engines.

First, it can cause keyword cannibalisation, which occurs when multiple pages from one single site compete for similar keywords. This harms the site's overall ranking in the process, by having portions of the site that do not offer any unique value to users, in addition to diluting the strength of signalling for the original source of content.

Having multiple pages also increases the risk of search engines picking up the wrong URL for indexing and appearance in search results. In turn, this can decrease user satisfaction, their time on the site, and your credibility.

Last but not least, too many duplicate pages can also waste 'crawl budget', or the resources search engines allocate to crawl pages. Instead of crawling and indexing new pages you actually want indexed, search engines may allocate all these resources towards the duplicate ones.

Canonical Tags: SEO Best Practices

Canonical tags need to be implemented correctly, or search engines can simply ignore them by virtue of the tag's inaccurate capture of what is convincingly the original piece of content, harming your SEO performance as a result. Here are some of the best practices to follow:

Use Only One Canonical URL per Page

Sometimes, canonical tags can be included in the HTML of a page twice – however, this can still confuse search engines. That's why it's important to make sure only one canonical URL is used per page. For instance, if you've already set the canonical tag using a CMS setting, you don't have to manually add it in again to your HTML.

Always Use Self-Referencing Canonical Tags

Search engines see non 'www' and 'www' URLs (for example, https://example.com vs https://www.example.com) as separate pages. So it's important to clarify your preferred URLs with self-referencing canonical tag signals.

Avoid Non-Existent or Redirected Canonical URLs

One common misconfiguration is pointing canonical tags to URLs that no longer exist or redirect to another page. This creates crawl inefficiencies and may cause search engines to drop the page from their index.

• Avoid canonical tags that point to a 404 (Not Found) page, or a chain of redirects.
• Ensure that canonical URLs are active and return a 200 (OK) status.
• Regularly test your canonical links using tools like Screaming Frog, or Google Search Console to catch and resolve these errors.

Use Cross-Domain Canonical Tags Strategically

For sites with syndicated content or those republished on a third-party website, cross-domain canonical tags help preserve the SEO authority of the original content. Ensure the third-party site agrees to respect your canonicalisation request, and monitor syndicated content regularly to check for compliance.

Monitor and Audit Your Canonical Tags Regularly

SEO is ever-changing – and as your website evolves, new pages, redirects, or updates can introduce canonical tag errors. So it's crucial to schedule regular audits using tools like SEMrush, Ahrefs, or Google Search Console.