21st.dev

Infrastructure and UI building blocks for hosted AI agents.

21st.dev provides the infrastructure and UI primitives that developers need to build, deploy, and manage AI agents for the emerging agentic internet — where agents are first-class participants that interact with APIs, services, and users autonomously. The platform enables developers to deploy agents as hosted, API-manageable services with sandbox configuration and tool access, reducing the infrastructure work required to expose agent capabilities to other systems or end users. It is compatible with popular AI SDKs, making it accessible to developers already working with existing agent frameworks. 21st.dev targets SMB and mid-market development teams and uses multiple underlying LLM providers. It differentiates through its focus on the deployment and interface layer for agents specifically — making agents accessible and manageable via API — rather than the model or framework layer.

Compliance

SOC 2

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Key Features

Hosted agent deployment: Provides managed hosting for AI agents, making them accessible as persistent services rather than requiring teams to manage their own infrastructure for each agent deployment.
API-based agent management: Exposes agents as simple, well-defined APIs so other systems and applications can invoke, configure, and interact with agents programmatically without custom integration work.
Sandbox configuration: Supports configurable sandboxes for agent execution, allowing teams to define the environment, tool access, and constraints within which each agent operates.
Tool support: Provides built-in support for equipping agents with tools — API access, web browsing, code execution — enabling agents to take real-world actions as part of their workflows.
AI SDK compatibility: Works with popular AI SDKs, lowering the adoption barrier for development teams that already have agent logic built on common frameworks.
UI building blocks: Provides frontend components and interfaces for exposing agent interactions to end users, covering both the backend infrastructure and the user-facing layer of agentic applications.

Use Cases

For developers deploying agents as managed services: A developer who has built an agent for a specific task — data research, document processing, customer interaction — uses 21st.dev to host and expose it as an API-accessible service without managing server infrastructure.
For teams building agentic products that need both backend and frontend: A small team building an AI-native product uses 21st.dev’s infrastructure and UI building blocks together, getting both the deployment layer and the user-facing components from a single platform rather than assembling them separately.

Pricing MODELS

Usage-based

Pricing Summary

21st.dev uses a usage-based pricing model with custom enterprise pricing for larger deployments. Specific usage-tier pricing is not publicly listed — developers can review current pricing on the company's website.