Spectre.css

Lightweight, responsive and modern CSS framework for faster and extensible development.

Angular Material

Angular Material is both a UI Component framework and a reference implementation of Google’s Material Design Specification.

Open source modular CSS framework providing great structure for building websites quickly

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

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

Smart CSS viewer tailored for Designers.

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

The most advanced responsive front-end framework in the world

Simple. Robust. Responsive. Flexible.

Responsive HTML5, CSS and JavaScript Framework

A rock-solid default for HTML5 awesome.

World’s smallest responsive CSS framework (398 bytes!)

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

Metro UI CSS a set of styles to create a site with an interface similar to Windows 8.

A minimalist CSS framework

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

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

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

Material Component Framework for VueJS 2

A phone carrier that is actually nice to you.

W2UI is a small JavaScript UI library with a complete set of widgets: layout, grid, sidebar, toolbar, tabs, fields, popup, utilities.