It should be noted that there are two major categories of detection software: free plagiarism checking tools and those intended for members and subscribers only. There is no secret that lower prices usually mean lower quality. So most of the times, people think that free services automatically mean doubtful quality services. And yet, we would rather say that the “members only” plagiarism checking tools and their free counterparts are meant for different purposes.
Plagiarism checking tools: free online services
The main use of free plagiarism checking tools is a quick search. Such search may be required for a professor who needs to ensure that his/her student’s paper is original. Such check may also be useful to a copywriter who wants to avoid auto-plagiarizing. There is no need in sophisticated algorithms to conduct such quick check. Thus, free plagiarism checking tools are usually very simple in their nature and scan only against available web content.
Plagiarism checking tools: paid services
“Members only” plagiarism checking tools are usually used when large sums of money or a reputation is at stake. The most common subscribers of such services are major colleges and universities as well as PR companies.
The main difference between paid and free plagiarism detection services is the level of complexity of the used algorithms. Paid plagiarism detection services, for instance, have access to the vast databases of academic papers and materials that are not posted on the Internet. “Members only” plagiarism checking tools do not mark as plagiarized such common phrases as “It depends” or “As far as we can see”, etc.