BuiltWith - Find out the technology behind websites

Wayland - Wayland is intended as a simpler replacement for X, easier to develop and maintain.

Wappalyzer - Wappalyzer is a technology profilers and leads data provider. Create lists of websites and contacts that use certain technologies.

Y Window System - Y Window System is a platform that allows you to improve the speed, working, and efficiency of the application in your operating system and helps you to increase the responsiveness of applications similar to any locally based app.

WhatRuns - Extension that helps you identify technologies used on any website at the click of a button.

XQuartz - The XQuartz project is an open-source effort to develop a version of the X.