If your site is exceptionally large, you can use the date based filters to view a sample of recently indexed pages in Google to see if there are any duplication issues amongst those pages.

Questions Answered by the Website Health Check Tool

• Is Google indexing your site? Are they quickly indexing your new pages?
  
• Do you have duplicate content pages getting indexed in Google?
  
• Do you have canonical URL issues?
  
• Are any of your pages in Google missing page titles?
  
• Does your server send correct error messages?

• Allow you to search for not just a site, but a site and a keyword, like -seobook.com seo-
  
• Add indexed page counts from all major global search engines (Google, Yahoo, Microsoft, Ask)
  
• Allow webmasters to grab results from any of the above 4 engines, or mix and match
  
• Make each data point we collect link to the source

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