PlagSpotter is described as 'revolutionary, online, duplicate content checker that allows users to put their webpage URLs in to start an Internet duplicate content scanning and detection process' and is an website in the File Management category. There are more than 10 alternatives to PlagSpotter, not only websites but also apps for a variety of platforms, including Windows, Android, Blackberry and Google Chrome. The best alternative is Unicheck. It's not free, so if you're looking for a free alternative, you could try Plagiarisma or PlagScan. Other great sites and apps similar to PlagSpotter are iThenticate (Paid), Plagius (Paid), Compilatio.net (Paid) and SCRiBBR Plagiarism Check (Paid).
Plagius - Plagiarism Detector is a software that analyzes documents on the Internet searching for occurrences of suspected plagiarism. It scans various document format like doc, docx, pdf. Plagius also makes searches and comparisons with local files.