I don't think there is a website that is the best . Just find a several websites and try them all . This is the best way to find copied content. Or you can copy one sentence from your content paste it to search engine , and find copied content.
copy one sentence from your content paste it to search engine , and find copied content. is very long procedure @AdelDevise
To avoid plagiarism your content, if you use the wordpress platform, you can install some plugin. Usually, this plugin can optimize easily, so no body can right click in your content.
I Googled your question and found these links: http://www.problogger.net/archives/...ine-services-for-checking-content-plagiarism/ http://www.clickonf5.org/11623/online-content-plagiarism-checker/ http://www.shoutmeloud.com/top-10-tools-to-check-for-content-theft.html
Copyscape is cool if you want to scan a site or domain, but they charge lots of money for checking 'offline sources' (why do they even call it like that? misleading). If you have to check content in your text files on your PC I would recommend going for PlagTracker, they have a free option as well as pay-per-check and unlimited subscriptions.
Swift,Thank you for the information about the plagTracker. I was just looking for such a place that I can copy the whole article and click to check it.