Plagiarism can …

> be embarrassing: "US election: Melania Trump 'plagiarised' Michelle Obama" (BBC News, 19th July 2016)

> get you flunked, even if you didn’t do it on purpose (so take extra care!)

> can cause trouble even years later und can harm your reputation, see: "Plagiarism affair of minister Annette Schavan (Germany): "The Chancellor Will Have To Reshuffle Her Cabinet"" (Spiegel Online 9th February 2013)

By the way: Your paper can already be regareded as plagiarism if single passages or ideas are copied from other sources without reference. So take care with your citations!

With these free tools you can test on a small scale what your profs do with professional tools.

Selection inspired by CHIP article CHIP-Artikel "Plagiate online prüfen – Diese Tools gibt es" (German)

"How to cite"