How do you eliminate duplicate content from being indexed by Google?

How do you eliminate duplicate content from being indexed by Google?
  • Setting your preferred domain: You can ask Google to just crawl and index one of them and you also remove all risk of duplicate content.
    Setting a preferred domain helps your site retain the link juice even when a backlinking site links to a non-preferred version of your site.
    after setting your preferred domain in Google Webmaster Tools, your next step should be to set up 301 redirects from all of the non-preferred domain links on your site to your preferred ones. This will help search engines and visitors learn about your preferred version.

  • Manually point to the canonical link for all the pages: Google recommends that you add a canonical tag to the preferred URL of your content. When a search engine bot goes to a page and sees the canonical tag, it gets the link to the original resource.

  • Set up 301 redirects: To reduce the impact of such duplicate content issues, set up 301 redirects. 301 redirects from the non-preferred URLs of a resource to their preferred URLs are a great way to alert the search engines about your preference.

  • By putting Noindex meta tag: The noindex meta tag tells the search engine bots to not index a particular resource. You can use the noindex meta tag to avoid having search engines index your pages with duplicate content.