The internet is full of pages with identical or similar content. In SEO, a distinction is often made between canonical pages and duplicates. But what is a canonical page? And what does it mean for your SEO efforts?
What is a canonical page?
A canonical page is the primary version of a URL that search engines should index. It is a tool to avoid duplicate content by telling search engines which page to focus on in search results.
Think of it as the original among copies.
When you have multiple pages with very similar content, it can confuse search engines. They don’t know which page to show in search results. This can result in your “link juice” (SEO value) being spread thinly across multiple pages instead of being concentrated on one strong page.
This is where the canonical page comes in. By using a rel=canonical tag in the HTML code of the duplicate pages, you tell search engines which page is the original and most relevant.
Example of canonical tag and identical pages
You have a webshop with a product that comes in different colors. Each color has its own URL:
- www.example.com/product/red
- www.example.com/product/blue
- www.example.com/product/green
Even though the URLs are different, the content on the pages is almost identical. In this case, you can choose one of the pages as the canonical page, e.g. www.example.com/product/red. On the other pages (blue and green), you then insert a rel=canonical tag that points to the red page.
What do canonical tags look like?
A canonical tag is a piece of HTML code that helps search engines understand which version of a page should be considered the primary one. It typically looks like this:
<link rel=”canonical” href=”https://www.example.com/canonical-page/” />
This tag is placed in<head> the section on a URL or web page to indicate which page is the canonical version. It is important that you place your canonical tag before </head> section.
In this example, the tag tells search engines that the page https://www.example.com/canonical-page/ is the preferred version of the page, even though there may be other pages with similar content.
The syntax of a canonical tag
- <link>: This is an HTML tag used to link to external resources.
- rel=”canonical”: This attribute specifies that the link points to the canonical version of the page.
- href=”https://www.eksempel.dk/kanonisk-side/”: This attribute specifies the URL of the canonical page.
Why are canonical pages important for SEO?
Managing duplicate content with canonical tags is important for both user experience and your website’s Search Engine Optimization (SEO). If your website has multiple pages with identical or nearly identical content, it can create confusion for both users and search engines.
However, if you use cannonical tags on identical pages or pages with very similar content, you can:
1. Avoid duplicate content problems
Duplicate content occurs when multiple pages on a website have identical or very similar content. This can confuse search engines and result in neither page ranking optimally. By using a canonical tag, you can point search engines to the primary page and avoid this problem.
2. Consolidation of link juice
When there are multiple versions of the same page (e.g. with different URL parameters), inbound links can be scattered between them. A canonical tag helps to collect link juice on the preferred page. This can strengthen its authority and improve its ranking in search results.
3. Improving the crawl budget
Search engines have a limited number of pages they crawl on a website within a given time frame. By using canonical tags, you can ensure that search engines focus on the most important pages, avoiding wasting your crawl budget on duplicates.
4. Signaling the preferred version to search engines
Canonical pages allow you to tell search engines exactly which version of a page you want them to show in search results. This is especially useful when you have pages with small variations in content or URL parameters.
Best practices for canonical tags and duplicate content
- Placement: Canonical tags should be placed in<head> the section on all pages that are duplicates or near-duplicates of the canonical page.
- One canonical page: There can only be one canonical page for any given piece of content.
- Self-referencing canonical tags: It is good practice to include a self-referencing canonical tag on the canonical page itself. This means that the tag points to the page itself.
Errors and misunderstandings about canonical pages
Although canonical tags are an effective tool in technical SEO, there are unfortunately some pitfalls. To get the most out of your canonical tags, it’s important to know the most common mistakes and misunderstandings so you can avoid making them.
1. Using 301 redirects instead of canonical tags
A 301 redirect is a permanent redirect that sends the user from one URL to another. While it is often used to deal with duplicate content, it is not always the most appropriate solution.
When you implement a 301 redirect, you tell search engines that the original page no longer exists and that all of its SEO value should be transferred to the new page.
Canonical tags, on the other hand, work differently. They allow both pages to exist, but clearly indicate to search engines which page should be considered the primary version.
2. Incorrect indication of the canonical page
A common mistake is to specify the wrong URL as the canonical page. This can happen by accident or due to a lack of understanding of how canonical tags work. Always make sure to double-check that you have specified the correct URL for the canonical page.
3. Using canonical tags on pages with unique content
Canonical tags are only intended for pages with identical or nearly identical content. Using canonical tags on pages with unique content can confuse search engines and prevent them from indexing the unique content correctly.
Tools to find and analyze canonical pages
- Ahrefs
- Google Search Console
- Screaming Frog
- Semrush
