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COSS UI

A modern UI component library built on Base UI for developers and AI-generated interfaces.

Visit COSS UI4.5

  • Rating

    4.5 / 5

  • Pricing

    Freemium

  • Difficulty

    Intermediate

  • Works on

    Web

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What is COSS UI?

COSS UI is a fresh component library built on top of Base UI, designed for developers and AI-assisted workflows. It provides modern, composable primitives and patterns that work well in hand-coded and agent-generated projects alike, giving React teams a solid foundation for clean, accessible interfaces without rebuilding every low-level component.

Pros: what COSS UI does well

  • Built on Base UI for a solid, accessible foundation
  • Designed for both human developers and AI-generated code
  • Modern, composable components that fit most React projects

Cons: where it falls short

  • Primarily useful for React / Base UI workflows
  • Newer library with a smaller ecosystem than established alternatives

Who COSS UI is for

React developers and design engineers who want a modern, lightweight component layer for apps, dashboards or AI-generated interfaces.

Who can skip it

Teams committed to fully managed design tools or non-React stacks.

What people use COSS UI for

  • Building React interfaces from accessible, ready-made components
  • Starting a new app with a full theme instead of styling every primitive yourself
  • Giving a coding agent components it can read and change easily

How to get started

  1. 1For a new project, run pnpm dlx shadcn@latest init @coss/style (bun, npm and yarn work too).
  2. 2In an existing project, add the primitives with pnpm dlx shadcn@latest add @coss/ui.
  3. 3Optionally add the agent skills with npx skills add cosscom/ui, then copy components from the docs as you need them.

COSS UI pricing

The components are free to copy into your project. The source is on GitHub, where the repository is listed under the AGPL-3.0 licence, so check the licence before using it in a closed-source product. See current prices on COSS UI's site

Checked 2026-10-19. Prices change, so double-check before you pay.

COSS UI FAQ: quick answers

What is COSS UI built on?
Base UI for the underlying primitives and Tailwind CSS for styling.
Who makes it?
The team at Cal.com. It is the official design system of Cal.com.
Do I install it as a package?
No. Like shadcn/ui, you get the source code: the shadcn CLI or a manual copy puts each component file in your own project.

COSS UI alternatives

Not sold on COSS UI? These do a similar job, and each card says what it has in common.

All AI Productivity resources

Open Source UI

Focus: next.js components, tailwind css and copy paste. Shares react components and ui library with COSS UI. Free (COSS UI: Freemium). Rated 4.7 (COSS UI: 4.5).

WebsiteFreeWeb
4.7Visit

Beautiful UI

Focus: ai ui, chat components and copy paste. Shares react components and design system with COSS UI. Rated 4.6 (COSS UI: 4.5).

WebsiteFree planWeb
4.6Visit

ProUI

Focus: shadcn ui, ui templates and next.js. Shares react components and design system with COSS UI. Rated 4.6 (COSS UI: 4.5).

WebsiteFree planWeb
4.6Visit

23rd

Focus: shadcn registry, svelte 5 and ui components. Shares react components with COSS UI. Free (COSS UI: Freemium). Rated 4.6 (COSS UI: 4.5).

WebsiteFreeWeb
4.6Visit

Shadcnblocks Vue

Focus: vue, shadcn ui and tailwind. Shares design system and developer tools with COSS UI. Rated 4.7 (COSS UI: 4.5).

WebsiteFree planWeb
4.7Visit

Warp

Focus: terminal, AI and command line. Shares developer tools with COSS UI. A desktop app, not a website. Adds macOS, Linux and Windows. Rated 4.7 (COSS UI: 4.5).

Desktop AppFree planmacOS, Linux
4.7Visit

Free alternatives to COSS UI

Want to spend nothing? These free picks cover similar ground.

Astryx Design System

Focus: react, stylex and open source. Shares design system and components with COSS UI. A framework, not a website. Free (COSS UI: Freemium). Rated 4.6 (COSS UI: 4.5).

FrameworkFreeWeb
4.6Visit

mcpcn

Focus: mcp apps, shadcn and chatgpt apps. Shares react components and ui library with COSS UI. A framework, not a website. Free (COSS UI: Freemium). Rated 4.3 (COSS UI: 4.5).

FrameworkFreeWeb
4.3Visit

Google Artemis

Focus: android, automation and ai agents. Shares developer tools with COSS UI. Free (COSS UI: Freemium). Rated 4.8 (COSS UI: 4.5).

WebsiteFreeWeb
4.8Visit

Agentfiles

Focus: obsidian, obsidian plugin and ai agents. Shares developer tools with COSS UI. Free (COSS UI: Freemium). Adds macOS, Windows and Linux. Rated 4.7 (COSS UI: 4.5).

WebsiteFreeWeb, macOS
4.7Visit

Ego Lite

Focus: ai browser, browser automation and ai agents. Shares developer tools with COSS UI. Free (COSS UI: Freemium). Adds macOS, Windows and Linux. Rated 4.7 (COSS UI: 4.5).

WebsiteFreeWeb, macOS
4.7Visit
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