21st: Infrastructure and UI building blocks for the agentic internet

Infrastructure and UI building blocks for the agentic internet

21st.dev is the largest React component registry for AI applications, used by 1.4M developers (200K 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.

Active Founders

Serafim Korablev

CEO / co-founder

One of the first full-time vibe-coders (since October 2023). Co-founder of 21st.dev, a UI components registry with over 1m users. Previously co-founded Rork.com (then a web app builder for Next.js), the first Telegram-native memecoin launchpad (multi-million exit), and Via, a cross-chain crypto routing protocol with $1.5B GTV backed by Naval, Safe, Sandeep, and others. Passionate about design and basketball.

Serafim Korablev

CEO / co-founder

One of the first full-time vibe-coders (since October 2023). Co-founder of 21st.dev, a UI components registry with over 1m users. Previously co-founded Rork.com (then a web app builder for Next.js), the first Telegram-native memecoin launchpad (multi-million exit), and Via, a cross-chain crypto routing protocol with $1.5B GTV backed by Naval, Safe, Sandeep, and others. Passionate about design and basketball.

Sergey Bunas

Founder

CS dropout. Senior Software Engineer at Deel (W19). Built Perplexity before Perplexity (Suggesty, 2022 — #1 Product Hunt, featured in Google's internal newsletter). Solo-built a Figma competitor pre-AI (Stage, 10K users). Cambridge AI hackathon winner (solo)

Sergey Bunas

Founder

CS dropout. Senior Software Engineer at Deel (W19). Built Perplexity before Perplexity (Suggesty, 2022 — #1 Product Hunt, featured in Google's internal newsletter). Solo-built a Figma competitor pre-AI (Stage, 10K users). Cambridge AI hackathon winner (solo)

YC Photos