Unfragile

For responsive web design, Bootstrap offers a prebuilt mobile-first grid system and components 1, and Tailwind CSS provides utility classes for building responsive layouts directly in markup 3. Other options include Mantine and SilicaUI for component libraries, and Galen Framework for automated testing of responsive layouts 467.

1
Bootstrapgetbootstrap.comverified and signed
Open source frontend toolkit with a prebuilt grid system and components for building responsive layouts.
Website Docs
for agents: responsive · framework · mobile-first
2
Tailwind CSStailwindcss.comwebsite read, tools not yet checked
Utility-first CSS framework whose composable classes let you build responsive designs directly in HTML.
Website Docs
+12 community tools built for it
3
Mantinemantine.devwebsite read, tools not yet checked
React component library with over 120 customizable components and hooks for building accessible web applications.
Website Docs Get started
+4 community tools built for it
4
SilicaUIsilicaui.comwebsite read, tools not yet checked
Tailwind-based component library with CSS-first styling and design tokens across React and vanilla HTML.
Website Docs
+1 community tools built for it
5
Galen Frameworkgalenframework.comwebsite read, tools not yet checked
Automated testing tool that checks the relative positions of page objects across different screen sizes and browsers.
Website Docs

Sources

1Bootstrap · The most popular HTML, CSS, and JS library in the world.getbootstrap.com · read 2026-10-29
3Tailwind CSS - Rapidly build modern websites without ever leaving your HTML.tailwindcss.com · read 2026-10-29
4Galen Framework | Automated testing of responsive designgalenframework.com · read 2026-10-29
6Mantinemantine.dev · read 2026-10-29
7SilicaUI The CSS-first Tailwind Component Librarysilicaui.com · read 2026-10-29

For agents: the 10 actions behind this answer

responsive · Bootstrap CSS verified and signed
css · tinycss2 verified and signed
· Tailwind CSS website read, tools not yet checked
Tailwind CSS is a utility-first CSS framework for rapidly building modern websites without ever leaving your HTML.
· Galen Framework website read, tools not yet checked
· Panda CSS website read, tools not yet checked
Build modern websites using build time and type-safe CSS-in-JS
· Mantine website read, tools not yet checked
A fully featured React components library with 120+ customizable components, hooks, and utilities. Build accessible web applications faster.
· Silicaui website read, tools not yet checked
The CSS-first Tailwind component library Base UI behavior, OKLCH design tokens, and one color variant size shape vocabulary across React, framework-neutral HTML, and vanilla JS.
· Magic UI website read, tools not yet checked
Beautiful UI components and templates to make your landing page look stunning.
· Sass-lang website read, tools not yet checked
Syntactically Awesome Style Sheets
· Pallets website read, tools not yet checked

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