Open Source Bootstrap Alternatives

Semantic UI is a free and open-source framework for HTML and CSS. The framework treats words and classes as exchangeable concepts. Classes use syntax from natural languages like noun/modifier relationships, word order, and plurality to link concepts intuitively. Semantic UI provides similar benefits to that of BEM or SMACSS style guidelines.

Tailwind CSS is a customizable, low-level HTML & CSS framework. With Tailwind CSS you can create unique UIs without having to write any CSS. The framework comes with pre-written CSS classes that you can add to HTML elements to build bespoke UI components, your way.

Foundation is a free and open-source HTML & CSS framework that can be used to build and design websites and web applicaitons in a structured way.

Bulma is a free and open source HTML & CSS framework based on Flexbox. With Bulma you can quickly design responsive websites with pre-built components that follows web standards and best practices. The framework provides an easy to understand class structure that makes it easy to design websites with well structured code. Bulma is loved by many, and used by more than 200,000 developers worldwide.

PureCSS is a free and open-source CSS framework with a minimal footprint. The entire framework and its modules weighs in at just 3.7KB minified and gzipped. With PureCSS web developers can craft responsive UI for websites that works for mobile as well as desktop. Since every line of the framework was carefully considered, you can rest assured that your page size will be kept to a minimal, and your website loads fast.

A modern responsive front-end framework based on Material Design. With Materialize CSS you can speedup your design and development process as most of the heavy lifting is done for you with default stylings that incorporate custom components. All principles of Material Design is incorporated into the framework and can be easily utilized with components and animations that provide better feedback to the users of your websites and applications.

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

new.css is a classless CSS framework to write modern websites using only HTML. The framework weighs in at jut under 5kb making it an extremely performant.

Cirrus.CSS is a component and utility centric SCSS framework designed for rapid prototyping of web sites and web applications. In total, Cirrus.CSS weighs in at 17.3kb GZIPPED and provides all the necessary components for creating forms, buttons, check boxes, inputs and layouts for mobile and desktop.

With OpenUserCSS you can change the look of other websites. OpenUserCSS contains a wide range of themes that are easy to apply, to make websites more readable.

Material UI is a free and open-source framework with React components for faster and easier web development. With Material UI you can build your own design system and get started with Material Design. The framework includes pre-built React components for almost all UI use-cases that are at your fingertips as soon as you install Material UI.