YC active company list audit

21st

21st: Infrastructure and UI building blocks for the agentic internet. Headquartered in San Francisco, CA, United States. Current operating status: active.

Oomira checked this YC company record against source evidence and keeps the current facts, observed dates, and provenance visible before the interactive app loads.

20 facts3 sources4 superseded claims

What changed in the audit

external name

1code by 21st.dev -> 21st
2026-06-12 · yc-oss record id 31123: field "former_names" includes "1code by 21st.dev"

external name

21st.dev -> 21st
2026-06-12 · yc-oss record id 31123: field "former_names" includes "21st.dev"

external name

ex: 21st.dev -> 21st
2026-06-12 · yc-oss record id 31123: field "former_names" includes "ex: 21st.dev"

external name

1code -> 21st
2026-06-13 · YC directory former_names includes "1code"

Summary: Infrastructure and UI building blocks for the agentic internet
Description: 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:...
Website: https://21st.dev
Hiring: no
Headquarters: San Francisco, CA, United States
Operating status: active
Industry: B2B

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