The Software Lets you Detect Duplicate content

Best site is www.copyscape.com is a plagiarism checker

In a perfect world there would be only one version of every document but in real life this is not true. A great example is online versions of newspaper sites. In one form or another they all publish exactly or close to the same information about events and facts.

This also applies to many other areas, say, recipes, fitness programs, diet programs, definitions, explanations and many others.

Search engines can penalize a sites ranking if it looks as though content has been taken from another site. However, these sites do sit in index and even rank very well. How can this be? Does it mean there are no filters?

Filters exist, but they are in a primitive form

Search Engine’s need lots of resources to check the entire internet. Therefore, engines use simple forms to uncover duplicate content.

How?

The most common pattern is links. In general engines check between two linked sites for duplicate pages/content. If they exist, then engines try to get rid of the duplicate - usually the one who links to the source site.

How does this work?

If website B (healthy news) republished an article from site A (health research institute) and puts a link from B to A for reference, search engines understands that site A is the original source and the site B has copied it. Site B is seen as dupe content website.