Here is the text of an email I sent to a user who expressed a concern that Rewordify.com might be used by students to plagiarize.
Creator of Rewordify.com
Thank you for writing in with your concern about Rewordify.com being used to plagiarize. I want to tell you my opinions and stance on the subject.
First, I want to tell you that I understand how you feel. I was a high school English teacher for eight years and I still work in a semi-administrative role in a large public high school. I had more than one meeting with a parent over plagiarized work that was submitted to me.
Based on my experience, I believe that it's very unlikely that "reworded" text will be good enough to get past an English teacher. Rewordify.com is basically a pretty dumb computer program that tries to replace words, but it cannot read or understand. The output is usually full of somewhat awkward wording and lots of other little subtle errors that should raise red flags with you.
Also, Rewordify.com serves to simplify and lower the reading level of text. Usually, students are looking for a way to take their writing and make it sound more intelligent and eloquent. Rewordify.com does the exact opposite, which I believe makes it a relatively unattractive option for purposes of plagiarism.
There are many sites on the Internet that will change words in text. (Do a Google search for "reword my paper.") If I were to shut down Rewordify.com, besides the great harm it would do to thousands of schools who use it every day, there are still dozens of other ways that unscrupulous students could present to you text that was untraceable to the original source.
When I taught, I addressed the issue of plagiarism by having my students write the bulk of their work in the classroom. If you are a teacher, you understand that you very quickly get to know just exactly how your students write, and you have their writing samples in your possession. If you then assigned a homework assignment or paper for students to complete on their own, and if they would turn in "rewordified" text from an online source, the plagiarized work should be immediately obvious to you.
If you suspected plagiarism, you would ask the student for his or her sources, which he or she would have to provide. Rewordify.com does not re-write; it simply changes some words to simpler ones. The sentence structure, style, and tone of the original source are left alone. It is highly likely that at least 80%-90% of the words of the original source are preserved exactly as they were originally written. Comparing the original and the "reworded" version should result in enough similarity between the source and the student submission to wholly support your claim of plagiarism.
Rewordify.com is used in over 100 countries by millions of people. I have received hundreds and hundreds of emails from tremendously grateful teachers and educators because of how the site gives their students a new way to read, understand, and learn. I understand and validate your concern that students might misuse the site for dishonest purposes. But, I believe that the good the site does far, far outweighs this downside.
Before the Internet, it was virtually impossible for a teacher to prove plagiarism unless he or she visited the local library. The same classroom practice that worked back then still works now: supervise your students carefully as they write and get to know their writing well. I am not implying that you do not do these things; it's simply my response to your concern.
I welcome any suggestions you have to help me combat the problem to which you refer. If you have a workable idea, please let me know, and I'll try to program it into the site.