21st

21st

21st.dev
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About

21st is a developer platform that provides the fastest way to add AI agents directly into applications. The platform offers an SDK that allows developers to define, deploy, and run AI agents with minimal infrastructure setup. Developers can integrate agents using popular frameworks such as Next.js, React, TypeScript, Python, and Node.js. 21st includes built-in features like chat interfaces, session history, tool execution, memory, and real-time streaming responses. The platform also manages backend components such as sandboxed execution environments, authentication, rate limits, and observability. With support for Claude Code and Codex runtimes, developers can build agents that interact with tools, files, and APIs securely. By handling infrastructure and deployment automatically, 21st enables teams to launch production-ready AI agents quickly.

About

Preloop is the open source AI agent control plane for agents that take real actions. It combines an MCP firewall for tool access, an AI model gateway for cost, safety, and attribution, policy-as-code with human approvals, runtime session observability, and audit trails in a single self-hostable platform. AI agents can deploy code, change infrastructure, move money, touch production data, and burn model spend in seconds, so Preloop helps teams control what agents can do, how much they spend, and which actions require human approval. It works with OpenClaw, Hermes, Claude Code, Codex CLI, Cursor, Gemini CLI, Windsurf, Cline, OpenCode, and any MCP-compatible agent or managed runtime. Access rules can inspect arguments and context, not just tool names, with CEL expressions for fine-grained conditions. Teams can start with observability, then layer in approvals and deny rules without SDKs or invasive app changes.

Platforms Supported

Windows Not Supported
Mac Not Supported
Linux Not Supported
Cloud Supported
On-Premises Not Supported
iPhone Not Supported
iPad Not Supported
Android Not Supported
Chromebook Not Supported

Platforms Supported

Windows Not Supported
Mac Not Supported
Linux Not Supported
Cloud Supported
On-Premises Supported
iPhone Not Supported
iPad Not Supported
Android Not Supported
Chromebook Not Supported

Audience

Software developers, startups, and product teams that want a fast and scalable way to build and deploy AI agents inside their applications

Audience

Platform, DevEx, security, and operations teams that need to govern production AI agents, control tool access, approve risky actions, and maintain audit-ready visibility

Support

Phone Support Not Supported
24/7 Live Support Not Supported
Online Supported

Support

Phone Support Not Supported
24/7 Live Support Not Supported
Online Supported

API

Offers API Not Supported

API

Offers API Supported

Screenshots and Videos

Screenshots and Videos

Pricing

Free
Free Version Supported
Free Trial Not Supported

Pricing

$290 per month
Free Version Supported
Free Trial Supported

Reviews/Ratings

Overall 0.0 / 5
ease 0.0 / 5
features 0.0 / 5
design 0.0 / 5
support 0.0 / 5

This software hasn't been reviewed yet. Be the first to provide a review:

Review this Software

Reviews/Ratings

Overall 0.0 / 5
ease 0.0 / 5
features 0.0 / 5
design 0.0 / 5
support 0.0 / 5

This software hasn't been reviewed yet. Be the first to provide a review:

Review this Software

Training

Documentation Supported
Webinars Not Supported
Live Online Not Supported
In Person Not Supported

Training

Documentation Supported
Webinars Not Supported
Live Online Supported
In Person Not Supported

Company Information

21st.dev
21st.dev/

Company Information

Preloop
United States
preloop.ai/

Alternatives

Alternatives

Tuning Engines

Tuning Engines

CerebrixOS
BAND

BAND

BAND.ai

Categories

AI SDKs Supported
UI Design Supported

Categories

Agentic AI Supported
AI Control Planes Supported
AI Governance Supported

Integrations

Amazon Bedrock Not Supported
Claude Code Not Supported
Cline Not Supported
Codex CLI Not Supported
Cursor Not Supported
Gemini CLI Not Supported
Grok Bot Supported
Hermes Not Supported
Mattermost Not Supported
Model Context Protocol (MCP) Not Supported
OpenClaw Not Supported
OpenCode Not Supported
React Supported
Slack Not Supported
Tailwind CSS Supported
Windsurf Browser Not Supported
YAML Not Supported
shadcn/ui Supported

Integrations

Amazon Bedrock Supported
Claude Code Supported
Cline Supported
Codex CLI Supported
Cursor Supported
Gemini CLI Supported
Grok Bot Not Supported
Hermes Supported
Mattermost Supported
Model Context Protocol (MCP) Supported
OpenClaw Supported
OpenCode Supported
React Not Supported
Slack Supported
Tailwind CSS Not Supported
Windsurf Browser Supported
YAML Supported
shadcn/ui Not Supported
Claim 21st and update features and information
Claim 21st and update features and information
Claim Preloop and update features and information
Claim Preloop and update features and information