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YC List Winter 2026

YC W26 · Active

21st

UI building blocks for the agentic internet

Class
Winter 2026
Status
Active
Industry
B2B
Location
San Francisco, CA, USA
Team size
3

Website

https://21st.dev

About

21st.dev is the largest React component registry for AI applications, used by 2M developers We provide the building blocks to create agent-powered apps: UI components, agent templates.