# coss ui

> Modern UI component library built on top of Base UI

coss ui is an open-source React component library built on Base UI designed for both human developers and AI coding workflows. It provides over 500 modular components and particles spanning form inputs, navigation, overlays, and feedback elements. It speeds up interface development by offering accessible, ready-to-use primitives that can be integrated directly into web projects.

Website: https://coss.com/ui

## What it is for

- Drop prebuilt UI components like dialogs, inputs, and tabs into React applications
- Build accessible web forms using native-compliant field, fieldset, and input components
- Provide standardized UI building blocks to AI coding assistants

## Features

- Extensive component catalog covering accordions, modals, tables, and date pickers
- Built on top of Base UI primitives for standard accessibility and behavior
- Over 500 individual particles and components available to browse
- Built-in support for light and dark themes
- Designed to be easily consumed by AI-assisted development tools
- Open-source repository hosted on GitHub

## Pricing

Free and open source

## Details

- Type: Web app
- Category: [Development](https://xiry.app/topics/development.md)
- Topic: [UI Components](https://xiry.app/topics/development/ui-components.md)
- Open source: yes
- Platforms: Web, Code library
- For: React and web developers building modern web apps
- Alternative to: shadcn/ui, Radix UI, Chakra UI
- Tags: react, ui components, base ui, design system, frontend, open source

## Why it was saved

- [@kalypsodesigns, 27 February 2025](https://www.instagram.com/p/DGkiVKcT0ju/): Speeds up UI development by providing modular, ready-to-use modern components across categories like buttons, dialogs, accordions, and inputs.
- [@pacovitiello, 15 May 2025](https://x.com/pacovitiello/status/1922971487209652235): Production-quality tree view pattern: nested folders, filter input, auto-expanding matches, drag-and-drop reordering.

## Compare

- [Alternatives to Chakra UI](https://xiry.app/alternatives/chakra-ui.md)
- [Alternatives to shadcn/ui](https://xiry.app/alternatives/shadcn-ui.md)

## Related

- [shadcn/ui](https://xiry.app/resources/shadcn-ui-1902): Copy-paste React UI components built with Tailwind CSS and Radix primitives. (Website, Open source)
- [Efferd](https://xiry.app/resources/efferd): Pre-built, responsive shadcn/ui blocks and layouts for React applications (Web app, Freemium)
- [Motion](https://xiry.app/resources/motion): Open-source animation library for React, Vue, and vanilla JavaScript (Website, Freemium)
- [React Bits](https://xiry.app/resources/react-bits): Open-source animated and interactive React UI components and backgrounds (Website, Freemium)
- [21st.dev](https://xiry.app/resources/21st-dev): Curated directory of crafted React, Tailwind, and shadcn UI components. (Website, Freemium)
- [lucide-animated](https://xiry.app/resources/lucide-animated): Open-source animated React icons built with Lucide and Motion (Web app, Open source)

Updated 3 October 2026. Page: https://xiry.app/resources/coss-ui

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