Building a polished user interface from scratch is slow, and most developers end up re-solving the same problems — buttons, modals, pricing tables — that thousands of other projects have already solved well. 21st.dev is a community-built catalog of React components designed to be pasted straight into a project or installed automatically by AI coding tools like Cursor, Claude Code, or v0, so you get a professional-looking UI piece without designing or coding it from zero. The registry holds 10,000+ components and templates compatible with the shadcn/ui ecosystem, shipped as AI-ready prompts. Beyond the component library, 21st also builds developer-facing infrastructure: Magic MCP (an MCP server integrating the registry directly into AI coding tools, 5,500+ GitHub stars) and a 21st SDK/Agent Elements for adding sandboxed, streaming AI agents with production-ready chat UI to applications. Pricing ranges from a free tier (2 component copies/day) to Builder ($6/month, unlimited copies) and Builder+AI ($15/month, plus AI credits); Team plans are $7.50/seat/month. It's a YC W26 company with users at Google, Meta, Shopify, and Vercel.
| # | Tool | Best for | Price |
|---|---|---|---|
| 1 | Design engineers et développeurs front-end qui construisent des sites web/apps avec React, TypeScript et Tailwind CSS | — | |
| 2 | Développeurs | — | |
| 3 | Développeurs | — | |
| 4 | Développeurs indépendants et petites équipes construisant un SaaS B2B sur Next.js/Remix | — | |
| 5 | React developers and product teams building production web apps | — | |
| 6 | Developers, QA engineers, and technical writers wanting Git-native API workflows | — | |
| 7 | React developers and product teams building custom onboarding UI | — | |
| 8 | Development teams building custom CRM/ERP software, often with AI coding assistants | — | |
| 9 | Développeurs construisant des systèmes polyglottes (Python/Node/Rust/navigateur) où la validation doit rester identique partout | — | |
| 10 | Développeurs construisant des panneaux d'administration, outils internes, écrans de configuration | — | |
| 11 | Développeurs Next.js construisant des sites de contenu ou e-commerce | — | |
| 12 | Développeurs et agences WordPress effectuant des migrations de sites | — |
A free library of pre-built, animated building blocks for websites — instead of a developer hand-coding a fade-in effect or a particle background from scratch, they copy a ready-made component into their project and adjust it, the same way people already
A production-ready Next.js SaaS boilerplate with auth, billing, multi-tenancy and admin dashboard already built, so you skip months of setup and start on your actual product.
600+ production-ready React + Tailwind CSS components, with a free open-source core and paid premium blocks.
Free, open-source, offline-first API workspace that stores requests as plain-text Markdown files versioned in Git.
Headless React library for product tours, onboarding hints and checklists.
Open-source TypeScript framework for building CRM/ERP apps, AI-coding-assistant friendly.
One schema file that validates data identically in Python, Node.js, the browser, and Rust — so a Python backend and a JavaScript frontend can't silently disagree about what a valid payload looks like.
A JavaScript library that asks users for structured data through a modal dialog with a single function call, like calling prompt() but for full forms.
An open-source, AI-native CMS for Next.js 16 with a visual block editor, Supabase backend, and built-in e-commerce.
A WordPress database search-and-replace tool that safely handles serialized PHP data, with a visual preview before anything changes.
