This tool crawls your entire site and then analyzes all your pages for duplicate content. It shows similarity percentage among all pages on your site, so you can see what pages are similar enough to trigger a flag in major search engines and consequently they can penalize your site for duplicate content.
The higher the similarity, the more likely that you will zapped by them
Below is its screenshot and I think the tool doesn’t require any how-to as it is quite simple.
If you have any comment, questions or anything else, please let me know.
You can download it here.
P.S – This tool is NOT intended for large websites and has a lot that can be improved.