YCW26· AI· Devtools21st
UI building blocks for the agentic internet
ActiveChecked 16h ago
Founders
- Serafim KorablevFounder/CEO
- Sergey BunasFounder/CTO
Same space
Adjacent
Overlapping tags, a different niche.
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About 21st
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.
San Francisco, CA, USA
21st: questions
Which YC batch was 21st in?
21st was in Y Combinator's Winter 2026 batch (W26).
Is 21st still active?
Y Combinator lists 21st as active.
Who founded 21st?
21st's founders, as listed on its YC page: Serafim Korablev (Founder/CEO), Sergey Bunas (Founder/CTO).
Where is 21st based?
21st lists San Francisco, CA, USA as its location on YC's directory.
Not affiliated with Y Combinator. From YC's public directory. Logos via logo.dev; trademarks belong to their owners.