How do anti-plagiarism softwares work?

Question

How do they tell if you committed plagiarism with all the endless ideas (or any literature stuff) you can take from others? How effective are they?

Answer 1

Well, usually the software is sold by an online site, that teachers upload their students work to an "archive" that archive is then used as a base to compare to other student works, by other teachers as well. And whats in the archive, is also compared to online archives of encyclopedias, dictionaries, almanacs, and sometimes have the cooperation of publishers (books, magazines, periodicals etc).

So, when a teacher uses this software, they upload their student's papers to the site, the site then searches these databases for simliar terms or phrases that appear in other works. Its based on a percentage match. the higher the perecentage, the more likely that the phrase was copied from another source.


The most popular one is:
http://turnitin.com/


Testimonials can be found on their website, but its trusted by many university professors and media outlets.

Answer 2

They are quite effective. They compare the submitted text to a database that has an extensive library of works, both professional and non-professional.
The software then filters out common phrases and expressions.
The remaining text is then matched with the database.
Any matches are flagged and graded on percentile of matched words.
These results are then given to the person who submitted the text, with all noted matches flagged.

Answer 3

http://plagiarismsoftware.org/