Using Canonical URLs Correctly

The URL of the main version of a page on a website is known as a canonical URL. This is specified using a canonical tag in the HTML of the page, which allows Google and other search engines to identify it as the primary version of the page content. Using canonical URLs correctly can improve the performance of a website in search engine rankings. If you want all the backlinks from different pages to go to one specific URL, you can use canonical URLs. This will also help improve your ranking, because multiple links from different pages will be consolidated into one stronger link. To do this, you can use the rel="canonical" tag in the header of your HTML code. Alternatively, your CMS might have a setting that allows you to specify canonical URLs without having to edit the HTML code. For example, if you're using Magento 1, you can follow these steps to specify canonical URLs for products and categories across your site. If you need to change the default self-referencing canonical tag on your Wix page, you can do so by going to Menus & Pages, hovering over the relevant page, clicking the show more icon, then going to SEO options > Advanced SEO, and clicking 'Add New Tag' under the Custom Meta Tags heading. Another way to change the canonical tag is to implement a rel="canonical" HTTP header. Google takes all the URLs listed in a sitemap into account when determining which URL is canonical. For example, if a URL ends in a trailing slash and you have an identical URL that doesn't have a trailing slash, Google may consider them to be two different pages. If you're implementing canonical tags and accidentally make a mistake, it's not unheard of. Make sure to use absolute URLs when referencing canonical tags, so they're properly interpreted. You should only set canonical URLs for duplicated or nearly identical content. If you're not sure, our Site Audit tool can flag duplicate content and recommend either adding a canonical tag or redirecting the page. If you want to fix canonical tag errors and many other issues, get started with the Semrush site audit tool. You can find more information at Siterush.com/site-audit tool.

(source: https://www.semrush.com/blog/canonical-url-guide)