21st.dev

✨Key Features

• ▸Massive UI Component Library: Thousands of beautiful, production-ready React components (chat inputs, AI prompt boxes, animated chats, hero sections, pricing tables, etc.) optimized for AI/agent interfaces.
• ▸Magic AI Agent: Describe what you need in natural language → get multiple UI variations instantly. Works as an MCP server with Cursor, Windsurf, and other AI coding tools.
• ▸21st Agents SDK: Full toolkit to build and deploy AI agents with built-in UI, memory, tools, observability, and managed infrastructure.
• ▸Agent Templates: Ready-to-use examples like lead research agent, support agent, docs assistant, Slack monitor, browser-use agent, GitHub repo explainer, etc. (Next.js, Python, Go starters available).
• ▸Built for AI Apps: Designed from the ground up for modern AI interfaces and agentic workflows.
• ▸Developer-Friendly: Open-source elements, huge community (1.4M+ developers, 200K MAU), easy integration, and works seamlessly with Next.js, Tailwind, and popular AI coding editors.
• ▸Backed by Y Combinator: Formerly known as 1code.