Duplicate websites have similar content as another website on the internet. Duplication of content in websites has become very common now with more and more similar websites popping up.
Websites that can have duplicate content:
Some ecommerce websites that display similar products, or real estate websites with similar properties listed can be considered as duplicate content websites. Many websites simply hack or scrap the content of a website to host a website in a different name. Websites using the black hat SEO technique of multiple doorway pages that land to the same homepage is also considered for duplicate contents. Affiliate websites that are similar found in plenty on the internet. Even blogs have great vulnerability to have duplicate content.
What are not duplicate contents:
Contents that are taken from the resource websites like wikipedia, quotes, coding syntax, formulas that is mostly generic are not considered for duplication. If a website is hosted in different languages then the content is translated to a different languages, here it is not considered duplicate.
How search engines find duplication:
Search engines use filters to find the duplicate content in websites. When a search engine crawls a website it stores the information about the content of a website for a particular set of keywords. Search engines use a filter by referring this content every time a website is indexed. Simply all duplicate or spam contents are filtered out from the search results.
Google says that it doesn’t prefer to alter the page rank of websites rather it's concentrating in providing non duplicate contents to its users.
Rather following the copy cat method, it better to be genuine to give relevant and fresh content for the users as well for the search engines.
