Having identical or similar content on more than one URL often results in SEO issues. Using a canonical tag helps in preventing issues arising out of duplicate or similar content appearing on multiple URLs.
Google identifies the duplicate versions to crawl sites
In case you have a single page that's accessible by multiple URLs, or different pages with similar content (e.g, a page with both a desktop and a mobile version), Google identifies these as duplicate versions of the same page and picks one URL as the canonical version to crawl that, while all other URLs will be considered duplicate URLs and crawled less often.
Using a canonical tag explicitly tells Google of the Master document
A canonical tag will act as a hidden message on a web page telling search engines that the content on a specific URL is just a copy or a duplicate of the master content. You can place the canonical tag in the header code of the master page on your site.
Note: Use a rel="canonical" link tag: to indicate when a page is a duplicate of another page, you can use a <link> tag in the header code of the master page on your site.
Here are the steps to follow:
- List down all your duplicate URLs (in notepad on your system)
- Create <link rel="canonical" href="your_duplicate_url"/> for all your duplicate URLs (in notepad on your system)
- Open header code of the master page on your site
- Paste links your have created in step 2
- Click on 'Save'