Copyscape is an online and free plagiarism checker of web pages. It checks the originality of content, prevents duplicates and searches for existing content.
Copyscape also offers two more professional solutions:
1. Copyscape Premium – more powerful plagiariasm detection with added features such as copy-paste originality checks, batch search, private index, case tracking and an API.
2. Copysentry – comprehensive protection for websites by automatically scanning the web for possible content theft.
Read more about Copyscape at www.copyscape.com