Duplicate content is one of the simplest ways to prevent any website from ranking, the problem is it can also get you banned or removed in extreme cases. It’s that important that Google has provided a full page explaining “what is” and “how to prevent”.
Many tools are available to help locate duplicate content one of the best ways is Google itself. Copy a string of text from a web page or word document and past it into the search bar. You will see any websites using the same copy.