Bootstrap

Simple and flexible HTML, CSS, and JS for popular UI components and interactions

Apache Cordova

Platform for building native mobile applications using HTML, CSS and JavaScript

Bulma is an open source CSS framework based on Flexbox and built with Sass. It’s 100% responsive, fully modular, and available for free.

Element, a Vue 2.0 based component library for developers, designers and product managers.

The most advanced responsive front-end framework in the world

A rock-solid default for HTML5 awesome.

Ionic is a cross-platform mobile development stack for building performant apps on all platforms with open web technologies.

A CSS Framework and a Set of React Components that Implement Google’s Material Design

Easily create apps using the web technologies you know and love: HTML, CSS, and JavaScript.

Polymer is a library that uses the latest web technologies to let you create custom HTML elements.

A set of small, responsive CSS modules that you can use in every web project.

A framework for building native apps with React

A UI Component library implemented using a set of specifications designed around natural language

Spectre is a web application to diff screenshots.

A lightweight and modular front-end framework for developing fast and powerful web interfaces