Canonical URL
A canonical URL tells search engines which version of a page is the main page when multiple URLs show the same or very similar content.
- It helps prevent duplicate-content issues by consolidating indexing signals to one preferred URL.
- Canonicals are especially useful for ecommerce websites who generally have many filters, query parameters, tracking parameters, paginations and other technical issues which may create duplicate content issues.
- A canonical URL is a directive, not a command - search engines usually respect the directive but may choose to ignore it in specific situations.
- Canonical URLs also help in consolidating ranking signals to the chosen URL.
- Bad canonicals can cause the wrong URL to rank or important pages to drop from search engine results, resulting in loss of organic traffic and visibility.
What Is a Canonical URL?
A canonical URL is the preferred version of a webpage that you want search engines to index and show in search engine result pages.
When your site has multiple URLs that load identical or near-identical content, search engines may treat them as duplicate content, which is a violation of Google search central quality guidelines.
The canonical URL helps you address the duplicate content issues by telling search engines - “If you find multiple versions of this page, this is the one I want you to consider as original page and display in search results.”
Canonical URLs are implemented using the rel="canonical" tag element inside a page’s <head> section.
Here’s a basic example of a canonical tag:
<link
rel="canonical"
href="https://example.com/preferred-page/"
/>
The goal is to keep your website’s indexing signals focused on one clean, consistent URL especially when parameters,filters, or alternate paths can create multiple versions of the same page.
Why Canonical URLs Matter for SEO
Canonical URLs help search engines understand which page should be treated as the “main” one when multiple URLs show the same or very similar content. Without this clarity, your pages with similar content or near identical content can start competeing with each other in search results. In the worst case, your website could be penalised for duplicate content issues and get de-listed from Google search if too much duplicate content is detected.
Here’s how canonical URLs are a very important part of your technical seo strategy:
- Avoids duplicate indexation: Search engines may index a parameter or alternate URL instead of your clean preferred URL. A canonical tag reduces that risk by ensuring it indexes the preferred version defined by you.
- Consolidates ranking signals: If multiple pages have similar content, backlinks, relevance, and other signals can get divided across them. A Canonical URL helps consolidate those signals toward one preferred page.
- Improves crawl efficiency: When crawlers don’t waste time crawling duplicate versions of a page, they can spend more time discovering and refreshing important pages on your website that matters to you.
- Helps the right URL rank: If your website has multiple versions of the same URL because of UTM links, product filters, query parameters etc - a canonical URL ensure the right person is ranked in search results and you get organic traffic on the preferred version (and not the one with query parameters or other filters in the URL)
- Creates a more consistent URL footprint: A consistent URL structure ensures your data is clean, which leads to better reporting in Google search console, Google Analytics and there are no long "mystery" URLs lurking around in your marketing dashboards and excel sheets.
Canonical URLs do not "boost rankings” or help you improve your organic traffic but they do prevent SEO value from being diluted across multiple URLs that may contain similar content.
Common Situations Where Canonicals Are Essential
Canonical URLs becomes an absolute necessity when your website can generate multiple URLs that show the same or nearly identical content. GIven below are some common situations when you should be using proper canonical urls to prevent duplicate content issues and ensure consistent, clean indexing happens.
Tracking parameters and campaign URLs
Let's say you have a page on your website whose URL is:
Your digital marketing team member may add UTM sources to this URL to be able to measure the traffic that visits the website through the weekly newsletter. After adding the UTM sources, the URL could look something like this:
Notice that both the URLs will essentially load the same page, and have the same content. And it is possible that search engines may choose to index the URL with the UTM parameters and not the "cleaner" one without the UTM parameters.
To prevent this from happenieng, all you need to do is insert the below code in the head section of the page -
<link
rel="canonical"
href="https://example.com/services/plumbing-hvac"
/>
This instruction tells Google that this url -
https://example.com/services/plumbing-hvac
is the original version and to be indexed
while this URL -
https://example.com/services/plumbing-hvac?utm_source=email&utm_medium=august-newsletter-weekly
is a copy and should be ignored.
URLs with Ecommerce filters, faceted navigation, and sort URLs
The above logic also applies to e-commerce sites with category pages, URLs with specific filters such as sorting and urls which supports faceted navigation. Such website structures can produce thousands of near duplicates because of presence of specific filters and query parameters in the URL. Common examples include URLs of this nature - ?color=black, ?size=9, ?brand=nike, ?sort=price_asc.
The presence of a Canonical URL helps you keep the main product or category URL in Google's index and set it as the preferred version for indexing.
Please note - There are specific situations when you may want a specific product URL to be indexed along with the main category URL. For example,
If your product category URL is https://www.example.com/headphones/pr?category=faaad0ce, and you want this page to be indexed and ranked for "audio products" and "headphones", then you need not put the parent URL https://www.example.com/headphones as a canonical URL in the category URL's source code.
You should instead use the category URL as the canonical URL, provided the category URL has enough content and serves a different purpose than the parent URL.
Same content accessible through multiple paths or duplicate routes
Some websites may allow the same page to be access through multiple URLs or different routes. This generally depends on the business case and what the website wants to achieve as a business outcome. For example, a website selling shoes may show the same content through a product page with the URL /product/blue-shoes and the URL /shoes/blue-shoe.
In this situation, it is advised to choose one consistent canonical to avoid duplication. Search engines should index only one route and not both.
Multi language and multi-regional sites - Combine Canonicals with Hreflang
If your website have content spread across different regions and languages, it is very common to have near identical pages differing only by language or region. For example, you may have the language code in the URL - /en/, /es/, /fr/ or /us/, /in/, /uk/ which can create duplicate content issues, if the individual URLs are not properly canonicalised.
The best practice in such situations is:
- Use hreflang to tell Google which language/region version to show to users.
- Use self-referencing canonicals on each language page (each page should canonical to itself) so search engines treat them as legitimate localized versions and not duplicates.
- Only use cross language canonicals in rare cases where pages are truly duplicates and you do not want localized pages to be indexed.
Other Technical Configurations
There are some technical configurations where canonicals become essential, some examples are given below
- HTTP vs HTTPS or www vs non-www - If the same URL is accessible through both http and https, then it is advised to define which version should be the canonical one.
- Trailing slash, uppercase/lowercase, and URL normalization issues - If the url is accessible with and without a trailing slash, it is a good practice to define which version should be the canonical URL. Although Googlebot and other search engines will most likely not consider this a duplicate content, but it is better to define things for absolute clarity.
- Mobile versions - If your website has a mobile specific website and URLs are accessible through two different versions (e.g example.com/page and m.example.com/page), it is advised to define the canonical in the source code.
- URLs with paginated content - If you have long form of content where the content spans across multiple paginated pages, you have to put canonical url in the paginated page to ensure there aren't any duplicate content issues.
- Staging links - If a staging site or development environment is publicly accessible, a canonical URL helps prevent indexing of staging links. A much better solution here is to block or restrict those staging links using authentication.
- Session IDs and other dynamic URL parameters - Some websites may append session IDs or other parameters that could create endless URL variations. A canonical URL helps keep indexing focused on stable, clean URLs.
Do's and Don'ts of Canonical URLs
Canonical tags are simple to add, but easy to get wrong. Use the checklist below to make sure your canonical URLs send clear, consistent signals to search engines.
Do's
- Use complete URLs: Always use the complete URL (including https:// and the domain), not relative paths.
- Self-canonicalize: Pages should usually have a canonical pointing to themselves to prevent duplicate content issues.
- Canonicalize URLs with parameters: URLs with UTMs and tracking parameters should typically canonicalise back to the main version.
- Canonicalize to the closest match: If two pages are similar, canonicalise to the most relevant page - not the homepage.
- Keep canonicals consistent: Match your preferred domain (www vs non-www), protocol (HTTPS), trailing slash, and casing rules.
- Eliminate redirects: Make sure the canonical URL does not redirect and isn’t part of a redirect loop or redirect chain.
- Ensure the canonical URL is indexable: The canonical page should not be blocked by robots.txt or through a robots meta tag.
- Use self-referencing canonicals on language pages: On multilingual sites, each localized page should normally canonicalise to itself (and use hreflang for language targeting).
Don’ts
- Don’t set multiple canonical tags: More than one canonical tag is unnecessary and may confuse crawlers.
- Don’t canonicalize unrelated pages: If the content isn’t a close match, search engines may ignore your canonical signal.
- Don’t canonicalize everything to the homepage: This can cause important pages to drop from the index or never rank properly.
- Don’t point canonicals to URLs with redirects: Canonical targets should be the final destination URL (200 OK status code), not a 301/302.
- Don’t create canonical chains: Avoid A → B → C. Always point directly to the preferred URL.
- Don’t mix signals: If canonicals point to one URL but your sitemap or internal links point to another, search engines may be confused.
- Don’t include tracking parameters in canonicals: Canonical URLs should be clean from tracking parameters and other filters.
- Don’t canonicalize to non-indexable pages: Avoid canonicals pointing to pages with a noindex robots meta tag, blocked by Robots.txtcked pages and error pages.
FAQs on Canonical URLs
No. A redirect sends users and bots to a different URL. A canonical keeps the page accessible but suggests which URL should be indexed..
It’s a good practice to self-canonicalize pages on your website to prevent duplicate content issues. That said, a canonical tag is not a mandatory tag and not having one will not have any effect in indexation or rankings."
Yes they are called cross-domain canonicals but it should only be used when content is genuinely duplicated across domains and you control the relationship between the two domains.
A canonical URL is a directive, not a rule. Search engines may pick a different URL for indexation other than the canonical, depending on the situations and signals that the search engine receives from other sources (including external domains).
In most cases, Yes. But there are specific situations when you may not want to canonicalise to the main page and would like the URL with specific parameters to rank.
The canonical tag is in a webpage's HTML's <head> section. This part of a page that contains meta information not usually seen by users but read by search engines.