# 21st.dev

> A community-driven library of UI components and AI agent templates with an SDK for building and deploying AI agents fast.

21st.dev is a platform that provides a curated library of open-source UI components and AI agent templates, alongside a dedicated Agents SDK for rapidly building and deploying AI-powered applications. Developers can browse, copy, and integrate ready-made React/Tailwind components directly into their projects, saving significant design and development time. The platform also offers an Agents SDK with built-in infrastructure including sandboxed execution, streaming, authentication, spend limits, and observability. Backed by Y Combinator, 21st.dev targets frontend developers and AI engineers who want to ship faster.

- **UI Component Library**: *Browse hundreds of community-contributed React components (chat UIs, inputs, animations, etc.) and copy them directly into your project.*
- **AI Agent Templates**: *Pre-built agent templates for common use cases like email agents, web scrapers, note takers, and monitoring agents — ready to deploy with minimal configuration.*
- **Agents SDK**: *A first-party SDK that provides built-in chat history, token streaming via SSE, spend caps, rate limits, and session replay/traces for AI agents.*
- **E2B Sandbox Execution**: *Each agent session runs in an isolated VM via E2B, ensuring secure and reproducible code execution.*
- **Magic Chat & 1Code**: *Integrated AI-powered tools for generating and editing UI components through natural language prompts.*
- **Observability**: *Session replay and distributed traces give developers full visibility into agent behavior and performance.*
- **Works with Claude & OpenAI**: *The Agents SDK supports both Anthropic Claude and OpenAI models out of the box.*
- **Community Contributions**: *Developers can publish their own components to the 21st.dev community and gain visibility through usage metrics.*

## Features
- UI component library
- AI agent templates
- Agents SDK
- E2B sandbox execution
- Token streaming via SSE
- Spend limits and rate limiting
- Session replay and observability
- Magic Chat UI generation
- 1Code AI coding assistant
- Community component publishing
- Claude and OpenAI support
- Chat history management

## Integrations
Claude, OpenAI, E2B, AgentMail, Convex, Slack, Atlassian Statuspage, Browser Use, Next.js, DuckDuckGo

## Platforms
WEB, API, DEVELOPER_SDK

## Pricing
Freemium — Free tier available with paid upgrades

## Links
- Website: https://21st.dev
- Documentation: https://21st.dev/agents/docs
- Repository: https://github.com/21st-dev
- EveryDev.ai: https://www.everydev.ai/tools/21st-dev