WebTech Detector is described as 'will let you know that which plugins and themes have been used to provide it that look and functionality. WebTech Detector will provide you all the details about plugins, along with the details of Wordpress parent and child themes'. There are nine alternatives to WebTech Detector, not only websites but also apps for Google Chrome, Firefox, Wordpress and Microsoft Edge. The best alternative is Wappalyzer, which is both free and Open Source. Other great sites and apps similar to WebTech Detector are WhatRuns (Free), What CMS (Free), PublicWWW (Freemium) and WPThemeDetector (Free).
Wappalyzer is a technographics data provider, uncovering technologies such as content management systems, customer relationship management, ecommerce platforms, advertising networks, marketing tools and analytics.
WhatRuns offers browser extensions that give you information on the technology being used on websites you visit. WhatRuns uses a proprietary recognition algorithm to detect even the latest web technologies and plugins.
What WordPress Theme Is That is a free online tool allows you to easily detect what WordPress theme a site uses (including parent and child themes). It will also detect what WordPress Plugins are being used.