Imagine you have lots of drawings, but some of them are very similar to each other. You decide to show your friend the best one and tell them:
"This is the drawing I really want you to see."
In the world of websites, sometimes there are pages that are very similar to each other too.
To help search engines like Google know which page is the "best" one that they should show to people searching, websites use something called a "canonical tag."
This tag is like telling Google:
"This is the page I really want you to pay attention to, even though I have other pages that are a lot like it."
It helps make sure people find the best page when they're searching for something online.
Examples of why you might use canonical link Product Variations
Imagine an online store has a product available in different sizes or colours. Each variation might have its own page, but they are essentially the same product. By using a canonical link, the store can tell search engines which version of the product page is the main one to show in search results.
Main page: https://www.example.com/product/blue-t-shirt
Variations: https://www.example.com/product/blue-t-shirt?size=S, https://www.example.com/product/blue-t-shirt?size=M
Canonical link on variations: <link rel="canonical" href="https://www.example.com/product/blue-t-shirt"/>
Print Versions of Web Pages
Some websites provide a printer-friendly version of their articles. These versions are great for printing but duplicate the original content. A canonical tag can be used on the print version to point back to the original web page.
Main article: https://www.example.com/news/article-12345
Print version: https://www.example.com/news/article-12345?print=true
Canonical link on print version: <link rel="canonical" href="https://www.example.com/news/article-12345"/>
Tracking Parameters in URLs
Sometimes, websites add special codes to their URLs to track where visitors come from or how they navigate the site. These URLs can create duplicates of the same page. By using a canonical link, the website can ensure that search engines focus on the main page without the extra parameters.
Main page: https://www.example.com/page
Tracked URL: https://www.example.com/page?source=newsletter1&campaign=winter
Canonical link on tracked URL: <link rel="canonical" href="https://www.example.com/page"/>
WWW vs. Non-WWW and HTTP vs. HTTPS
Websites might be accessible with or without "www" in their address, or through both HTTP and HTTPS. These variations can create duplicates for search engines. A canonical link helps specify the preferred version of the website's URL.
Preferred URL (HTTPS and WWW): https://www.example.com
Alternative URLs: http://www.example.com, https://example.com, http://example.com
Canonical link on all versions: <link rel="canonical" href="https://www.example.com"/>
Session IDs in URLs
Online stores and other websites sometimes add session IDs to URLs to track visitors' sessions. These IDs make URLs unique to each visitor, potentially creating many duplicates of the same page. A canonical tag can point all these URLs back to a single, standard page.
Main shopping page: https://www.example.com/store
Session-specific URL: https://www.example.com/store?session_id=12345
Canonical link on session-specific URL: <link rel="canonical" href="https://www.example.com/store"/>
These examples help manage and consolidate duplicate content, ensuring search engines index and rank the most relevant and authoritative page.
Overall, canonical links are a fundamental SEO tool for maintaining clean, efficient, and user-friendly navigation of a website, both for users and for search engines' crawlers.