YC W26

21st

Infrastructure and UI building blocks for the agentic internet

About

21st.dev is the largest React component registry for AI applications, used by 2M developers (370K MAU). We provide the building blocks to create AI agents and agent-powered apps: UI components, agent templates, and an SDK with built-in UI, tools, memory, observability, and managed infrastructure.

Founders

Serafim Korablev
LinkedIn Twitter
Sergey Bunas
LinkedIn Twitter

Family Office Investors

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Industry & Focus

B2BEngineering, Product and Design