Wappalyzer - Wappalyzer is a technology profilers and leads data provider. Create lists of websites and contacts that use certain technologies.
WPThemeDetector - WordPress Theme Detector is a free tool that allows you to find details about a WordPress...
BuiltWith - Find out the technology behind websites
WPdetector - WPdetector is a free tool that helps users find out the theme and plugins used by a WordPress website. In short, it is a theme detector and a wp plugin detector. WP Detector also shows additional information about the website and its domain.
PublicWWW - source code search engine
Themesinfo WordPress Theme Detector - Themesinfo WordPress Theme Detector is one of the legit tools that is made to detect the installed WordPress themes and Plugins without any hassle.