SiteStacks is described as 'by Siftery is a helpful tool for discovering the technologies used by various websites' and is an website in the Development category. There are more than 10 alternatives to SiteStacks, not only websites but also apps for Google Chrome, Firefox, Self-Hosted solutions and Microsoft Edge. The best alternative is Wappalyzer, which is both free and Open Source. Other great sites and apps similar to SiteStacks are BuiltWith (Freemium), WhatRuns (Free), What CMS (Free) and Shraga (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.
A cross platform cross browser multi purpose tool for web developers, designers & webmasters: explore technologies in a website, manipulate web page content, extract data and more, all in a single simple to use bookmarklet based tool.
Rescan.io, previously Allora, builds lists of websites based on technologies they use. It's easy as 1,2,3: 1. Search for your competitor's tech. 2. Download the list of your prospect customers 3. Turn them into your customers!