Updated April 29, 2026
21st.dev is the largest React component registry for the agentic internet — an open-source, community-driven marketplace of shadcn/ui-based React + Tailwind components, blocks, and hooks. 1.4M developers (200K MAU), pivoting into a full agent deployment SDK.
Google's Agent Development Kit (ADK) is a modular framework for building AI agents that integrates natively with Gemini models and Vertex AI. It supports multi-agent architectures, tool use, memory, and deployment to Google Cloud, providing an end-to-end solution for building agents in the Google ecosystem.
Core capabilities each platform advertises.
What each tool does well, and the limitations to keep in mind.
Pros
Cons
Pros
Cons
Saves so much time — broad set of high-quality, free components, including 3D. Smooth React and Next.js integration.
Read full reviewChoose 21st.dev if you wantChoose if you want
Choose Google ADK if you wantChoose if you want
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