Explaining what website canonical URL link tags are and how to implement them correctly
If you want to be found on the internet, you need to make sure that your website optimisation accounts for Google’s algorithm. There are important ranking factors to help Google notice and reward your business with high search rankings, and one of these is canonical tags. Let’s break down what these are, and why getting on top of canonical URL best practices is so crucial for your success in the digital marketplace.
Key Takeaways
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Canonical URL tags are HTML hints (rel=”canonical”) that tell search engines which version of duplicate or similar content is preferred.
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Best applied to parameter-rich or duplicate URLs to consolidate ranking signals without using redirects.
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Incorrect use, such as canonicalising redirect pages, mixing signals, or placing tags in the body, can confuse search engines.
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Canonical tags live in the
section and should be consistent across similar pages, never set to a noindexed URL. -
Regular technical audits ensure canonical tags remain correctly implemented and effective.
Canonical (General Definition & Etymology)
Definition of canonical:
The term “canonical” generally refers to something that is recognized as authoritative, standard, or accepted as genuine. It is used in various contexts, including literature, religion, mathematics, law, and web development.
- Literature & Media: In storytelling, a “canonical” work refers to content that is officially part of a given universe or series, distinguishing it from fan fiction or alternative versions.
- Religion: In religious contexts, canonical texts are those accepted as part of an official doctrine, such as the biblical canon.
- Mathematics & Logic: In mathematics, a canonical form represents a standard or simplest form of an equation or structure.
- Law: In legal terms, “canonical” can refer to church law or widely accepted legal principles.
- Websites and SEO: In SEO, a canonical URL is the preferred version of a webpage when multiple versions exist, helping search engines avoid duplicate content issues.
Etymology of “canonical”:
The word canonical originates from the Latin canonicus, meaning “according to rule,” which itself comes from the Greek kanon (κανών), meaning “rule” or “measuring rod.” The term was historically used to describe texts, laws, or principles that followed an established standard.
Its meaning has evolved over time, maintaining the core idea of something being official, recognized, or authoritative in different disciplines.
What is a canonical URL tag?
Google hates duplicate content, and will automatically index just one web page if it finds multiples, making a decision on which page is the original. The thing is, you don’t want Google making this call for you. The algorithm won’t necessarily get this right, and leaving it up to chance risks undoing the hard work you’ve put into search engine optimisation in other areas. A canonical URL tag is a small piece of HTML code, which is implemented in order to indicate to search engine crawlers which page they should take as the original, and ensure that your efforts to improve SEO aren’t cannibalised by duplicate content on other pages.
What does a canonical URL tag do?
When the same or similar content appears on multiple pages, providing a canonical URL tag (rel=”canonical”) in the metadata of a URL indicates to Google which page you want to be crawled and indexed, and means you’re in control of deciding which web page contains your most important content. It signposts to Google which page is the one to count, and expedites the process.
Even if you don’t think your website has duplicate content, the fact is it almost certainly does. User sessions, product filters, capitalised letters, serving content at locations with and without www, all of these instances create what’s called parameterised URLs, which Google technically categorises as separate, and therefore duplicate pages.
The History of Canonical URL Tags
Canonical URL tags have played a vital role in SEO since their introduction in 2009, helping website owners tackle one of the most common challenges in digital marketing: duplicate content. Prior to their implementation, search engines struggled to determine which version of a webpage to rank when identical or similar content appeared on multiple URLs. This led to lower rankings, as search engines were unsure which page was the “authoritative” source.
Canonical tags were introduced by Google as a solution to this problem. They allow webmasters to indicate the preferred version of a page by adding a simple HTML element within the page’s header. This tag points to the “canonical” or original version, signalling to search engines that other similar or duplicate pages should not be indexed as separate entities.
The introduction of canonical tags quickly became a game-changer for SEO professionals, as it provided a way to consolidate link equity and avoid potential penalties for duplicate content. The tag allowed for better control over how search engines interpreted and ranked content, ultimately enhancing a site’s visibility and performance in search engine results pages / SERPs.
Since their introduction, canonical URL tags have evolved with the changing landscape of SEO, adapting to new technologies and approaches. They’ve become an integral part of modern SEO strategies, particularly for e-commerce websites and large-scale content sites, where managing duplicate content is a regular challenge. Today, canonical tags remain a crucial tool for ensuring search engines understand which content should be prioritised, helping brands avoid ranking issues and boost their SEO performance.
What is a canonical URL link example?
A canonical URL is the preferred version of a webpage when there are multiple pages with similar or duplicate content. By specifying a canonical URL, you inform search engines which page to index and rank, preventing penalties for duplicate content.
For example, let’s say you have two pages with nearly identical content, one accessible via https://www.example.com/product?item=123 and another at https://www.example.com/product/123. Even though both URLs lead to the same product page, you would use a canonical tag to tell search engines that the preferred version of the page is https://www.example.com/product/123.
In the HTML code of the duplicate page (https://www.example.com/product?item=123), you would add the following canonical tag in the <head> section:
<link rel=”canonical” href=”https://www.example.com/product/123″ />
This tells search engines that https://www.example.com/product/123 is the “canonical” version of the page, helping to consolidate link equity and ensure the page ranks properly.
How canonical URL link tags can be helpful your website’s SEO
Canonical tags aren’t just nice to have, they’re an essential part of an effective technical SEO strategy. With CMSs, http and non-https variants of the same page, along with optimised mobile website versions, you can quickly start racking up duplicate versions of pages. Canonical URL tags can be used to make sure your Search Engine Optimisation / SEO doesn’t suffer because of this. Here are just a few reasons why.
You choose the canonical tag
Especially if you’re using a CMS (content management system) like WordPress or if you have a separate mobile site, you may find that different pages with the same content end up having discrete URLs which aren’t the same. By far the easiest and fastest way to make sure that Google indexes the URL you want is to choose that version for it, using a canonical tag. Being proactive in this regard avoids any potential penalisation by the search engine algorithm.
Duplicate content can spoil your rankings
The problem with duplicate pages is that, as we mentioned, Google really doesn’t like them. For it and other search engines, it’s an indicator that a site isn’t producing unique, high quality content, which it views as an indicator of authority and trustworthiness. Especially if you run an eCommerce online store, but for any website, duplicate content can start to outrank the page you want getting the top spot on Google and especially on page one, and can even risk Google missing some of your other content as it crawls non-canonical duplicates.
Crawl budgets aren’t limitless
A crawl budget refers to how many pages of your website a search engine will crawl on your site, and how quickly it wants to do it. If you have lots of duplicate content, but you haven’t nominated a canonical URL, your crawl budget may get wasted as Google searches through duplicate content instead of indexing the other valuable content you’ve produced.
Consolidated link signals have more impact
Bringing your link signals onto one consolidated page can help you improve the ranking for that canonical URL, rather than splitting up your ranking power across lots of similar pages.
There are five types of canonicalisation signals:
- HTML tag (rel=canonical)
- HTTP header
- XML Sitemap
- 301 redirects*
- Internal links
A link signal is basically a way to tell Google that all similar content pages are linked back to their parent page — the canonical one. By making sure all link signals point back to the page with a canonical link tag, you boost this page’s chances of hitting the top spots on Google.
Canonical URL Link Tags Best Practices
Okay, so we’ve convinced you that canonicalised URLs are the way to go – so what’s the best practice when it comes to setting up canonical link tags across your online content? Let’s get into it.
Canonical tags can be self-referential
In fact, they should be. Self referencing tags reference the URL of the given page itself, and this avoids any confusion on Google’s part. While it’s not completely necessary to do so, the fact is that Google experts recommend this as best practice, because it makes it crystal clear which page you want to be indexed.
Canonicalise cross-domain duplicates
If you’re syndicating content, canonical URL links also stop cross-domain duplicate issues from arising. Using a cross-domain canonical tag will reduce the risk of any incidents of syndication outranking your original content, and make sure that you earn the authoritative reputation you deserve.
Be careful in canonicalising near-duplicates
The point of canonical URLs is to clearly indicate the preferred version of a web page, and to designate it as the definitive version to be counted by search engine crawlers. If you have near duplicate pages, and you’re tagging them both as the canonical version, your efforts will start to become self-defeating. The best practice for canonical URL links is to only ask the algorithm to find and reward one example of the content, so avoid overdoing it when tagging pages which are substantially similar or near duplicates.
Avoid mixed signals
You want your link signals on duplicate and similar pages to uniformly point back to one canonical URL. If you start to use mixed signals, Google’s algorithm can become confused, and your rankings will suffer. Again, the point here is to make it simple for Google to reward your other search engine optimisation efforts, so it’s best practice to choose one of the five canonicalisation signals, and be consistent when using it across your site.
Spot check your dynamic canonical tags
Regular website audits are also best practice, for a whole number of reasons. No matter how carefully you update your website and add new pages, products or content, the fact is dynamic canonical tags can become untethered from their original purpose. Make sure you regularly perform spot checks to make sure these technical aspects of your SEO are in good shape and are getting you the results you want.
The basics of canonical URL tag implementation
Once you’ve got the best practices for applying canonical URL tags down, you’re ready to start streamlining your website for Google and other search engine crawlers to find and reward your most authoritative content. Before you start applying rel=”canonical” to every URL, there are some basic issues you’ll want to avoid when it comes to implementation.
Avoid canonical loops and chains
Imagine that a canonical tag acts as a trusted expert who ‘endorses’ the right version of a page for the benefit of Google. The algorithm is looking for a sign from this expert that says, “Hey! I’m page Y, but the best source of this content is actually on page X. I recommend you visit page X and hear what they have to say!”. “Great”, thinks Google’s crawler, and it heads over to page X to start indexing away. Now, imagine that page X also has a message for Google, which is “Hi! I’m page X, but you actually want page Z”. Google then heads to page Z, which agrees that it is the best version of the content.
This is a canonical chain, and if you just felt some confusion reading that, imagine how quickly it can bamboozle a machine primed to trace canonical tags back to one trusted source. Chains, like the one illustrated in that example, and loops, where canonical link tags send search engine crawlers in a circular motion from page X to Y to Z and back to X again, are going to completely undermine your efforts to help Google’s algorithm reward your best content.
Don’t block canonicals via robots.txt
As part of technical SEO frameworks, a robots.txt file will help search engine crawlers know where to go and not to go within your site’s architecture. If you disallow URLs in robots.txt, it can’t tell Google and other search engines to read your canonical URL link tags, and it won’t consolidate link signals from different pages. To make sure your tagging efforts are rewarded, ensure canonical URLs are allowed via robots.txt files.
Multiple canonicals on one page
If you use more than one canonical tagged URL on a page, Google will simply ignore them both. This isn’t a crude tool which can be sprinkled liberally throughout all of your metadata for infinite search engine optimisation. Be strategic when using canonical tags, and you’ll be that much more likely to make sure they work in the way you want them to.
How To Implement Website Canonical URL Link Tags for Pagination Pages?
When dealing with pagination, implementing canonical tags correctly helps search engines understand how paginated content relates to the main version of the page.
Here’s how to do it properly:
1. Avoid Pointing All Paginated Pages to Page 1
A common mistake is setting every paginated page (e.g., /page-2/, /page-3/) to have a canonical tagged URL pointing to the first page (e.g., /page-1/). This can confuse search engines and lead to improper indexing.
Best Practice: Each paginated page should have a self-referential canonical tagged URL, meaning:
- /page-1/ → <link rel=”canonical” href=”https://example.com/page-1/” />
- /page-2/ → <link rel=”canonical” href=”https://example.com/page-2/” />
- /page-3/ → <link rel=”canonical” href=”https://example.com/page-3/” />
2. Use Proper Pagination Markup (Optional but Helpful for SEO)
Google no longer requires rel=”prev” and rel=”next” tags for pagination, but using structured data like breadcrumbs can help improve crawling and user experience.
3. Ensure Strong Internal Linking
Linking between paginated pages (e.g., “Next” and “Previous” buttons) and linking to the primary category or listing page can further reinforce the structure.
4. Consider Infinite Scrolling or Load More (If Applicable)
If your site uses infinite scrolling, ensure search engines can still access individual pages by providing paginated URLs in your sitemaps or using JavaScript-friendly SEO practices.
By following these steps, your paginated content will remain search-friendly while avoiding duplicate content issues.
What to avoid with canonical URL tags?
Canonical tags are best deployed when you have lots of URLs with very similar or identical page content. They help Google reward you for your genuine SEO efforts, and stop search engines from missing vital content while they waste time crawling identical versions of the same information. You want your canonicalised URL to be the most authoritative version of the content.
So there are some things you should never do:
- Never canonicalise a redirect page, as this can cause search engines to ignore or misinterpret your canonical tag.
- Never use hreflang tags to point to non-canonical tagged URLs, as this can also mislead Google.
- Don’t apply canonical tags to the same or very similar pages, but instead pick one authoritative version.
- Don’t use different canonicalisation signals across your website, but be consistent to avoid search engine crawler confusion.
- Never set a canonicalised URL to ‘noindex’, as these are contradictory commands. While it is likely Google will go with your canonical tagged link over the ‘noindex’ tag, it’s not good practice to include both.
- Do not use rel=”canonical” in the body of a webpage. It should only be used in the <head> section, and will be ignored if it’s not here.
What Does “Canonicalised URLs” Mean?
A canonicalised URL refers to a webpage URL that has been designated as the preferred version when multiple URLs contain similar or duplicate content. This is achieved using the <link rel=”canonical” href=”URL” /> tag, which helps search engines identify which version should be indexed and ranked.
Why Are URLs Canonicalised?
Canonicalisation prevents duplicate content issues and consolidates ranking signals by directing search engines to a single authoritative URL.
This is important when:
- A website has multiple URL variations for the same content (e.g., with and without www, HTTP vs. HTTPS).
- Product pages exist with different URL parameters (?color=blue or ?sort=price).
- A page is accessible through multiple paths (e.g., /category/product/ and /product/).
Example of a Canonicalised URL:
If a product page has multiple versions:
- https://example.com/shoes?color=red
- https://example.com/shoes?color=blue
You can canonicalise them to the main version:
<link rel=”canonical” href=”https://example.com/shoes/” />
This tells search engines to treat https://example.com/shoes/ as the main page and pass ranking signals from the variations to it.
Why Is Canonicalisation Important for SEO, and Why Can It Be Bad If Done Incorrectly?
Canonicalisation itself is a best practice for SEO, but incorrect implementation can harm your website’s rankings and indexing.
Here’s why:
1. Loss of Rankings Due to Incorrect Canonical URL Tags
If you mistakenly set a canonical tagged URL link pointing to the wrong URL, search engines may ignore important pages, causing them to be deindexed or not ranked.
- Bad Example: If every paginated page (/page-2/, /page-3/) points to /page-1/, search engines might not index deeper pages, reducing their visibility.
- Fix: Each paginated page should self-canonicalise to itself.
2. Duplicate Content Issues If Canonical URL Tags Are Missing
If multiple URLs serve the same content without a canonical tag, search engines may treat them as duplicate pages, splitting ranking signals across different URLs instead of consolidating them.
Example:
- https://example.com/shoes
- https://example.com/shoes?sort=price
- https://example.com/shoes?color=red
Without canonicalisation, Google might not know which version to rank, diluting SEO performance.
- Fix: Use <link rel=”canonical” href=”https://example.com/shoes/” /> to specify the preferred URL.
3. Wasted Crawl Budget
Search engines have a crawl budget, meaning they allocate a limited number of pages to crawl per site. If multiple URL versions exist without canonical tags, search engines waste time crawling duplicate pages instead of indexing new, valuable content.
- Fix: Implement correct canonical tags and block unnecessary URLs in robots.txt if needed.
4. Conflicts With Internal Linking or Redirects
If your internal links or redirects point to URLs that don’t match the canonical version, search engines may become confused, reducing the effectiveness of canonicalisation.
- Fix: Ensure internal links and redirects match the canonical version of the URL.
Just some final thoughts on Canonicalisation
Canonicalisation is not bad for SEO. It’s essential for managing duplicate content. However, misusing canonical tags can lead to ranking drops, deindexing, or wasted crawl budget. The key is accurate implementation to ensure search engines consolidate ranking signals correctly.
Need an SEO expert to handle your canonical URL tagging?
If you’re still not quite sure what the best practice is for canonical tags, or how best to implement them, don’t panic! The fact is, even SEO service agency experts take years to master the tricks and tools of the trade to implement this technical element of search engine optimisation, and it takes a lot of technical skill, know-how and regular spot checks and audits in order to make sure that your canonicalised URLs are correctly identified and are picked up by Google’s crawlers.
At Online Marketing Gurus, we have nearly a decade of experience in online digital marketing and crafting bespoke SEO strategies for businesses of all sizes and types. Whether you’re an eCommerce online store website struggling to win the day with an algorithm that’s confused by multiple parameterised URLs caused by filtering, or a website serving the same content on pages with different variants, we can help you get on top of your on-page SEO efforts and technical SEO to keep a consistent approach to canonical tagging that can help increase your domain authority in your industry.
If you’re ready to turn the task of managing canonical tags over to a professional, our team of Gurus is here to help. Talk to us today about how our services can boost and improve your SEO rankings on Google and get you noticed by the right audience, at the right time.
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About the Author
Andrew Raso
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