As a website gets bigger, it’s often hard to prevent pages from becoming duplicates or near-duplicates of each other. This can cause duplicate content issues. If you have two similar pages, and they are both eligible to rank for a certain keyphrase, the search engine simply doesn’t know which of the two URLs it should send the traffic to. To solve this, you can select a preferred URL, this is what we call the canonical URL.

Same content, multiple URLs
A canonical URL is a technical solution for duplicate content. You might, for instance, have a post or product that is attached to two categories and exists under two URLs, like so:

https://example.com/black-shoes/black-and-red-shoes/
https://example.com/red-shoes/black-and-red-shoes/
If these URLs are both for the same product, choosing one as the canonical URL tells Google and other search engines which one to show in the search results.

Canonicals also enable you to point search engines to the original version of an article. Let’s say, you’ve written a post for another party that is published on their website. If you’d like to post it on your site too, you could agree on posting it with a canonical to the original version.

great post by all thanks

Canonical URL: the search engine friendly URL that you want the search engines to treat as authoritative. In other words, a canonical URL is the URL that you want visitors to see.

Thanks to share here experienced guys,

the search engine friendly URL that you want the search engines to treat as authoritative. In other words, a canonical URL is the URL that you want visitors to see. Quite often canonical URLs were used to describe the homepage.

A canonical link element is an HTML element that helps webmasters prevent duplicate content issues in search engine optimization by specifying the "canonical" or "preferred" version of a web page