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21st.dev

21st.dev · San Francisco, CA, USA · founded 2024 · team 3 (small team, per YC profile) · Seed (Y Combinator Winter 2026 batch) · trust 0/4

Infrastructure and UI building blocks for the agentic internet - an open-source community & marketplace of premium React UI components, plus a CLI tool for AI coding agents to fetch components/skills.

This dossier was built by Clark from a public scan on 2026-07-04 and is unclaimed. Is this your startup? Claim it.

Verified facts

Company name21st.dev
source: https://www.ycombinator.com/companies/21st and https://21st.dev
Tagline / descriptionInfrastructure and UI building blocks for the agentic internet - an open-source community & marketplace of premium React UI components, plus a CLI tool for AI coding agents to fetch components/skills.
source: https://www.ycombinator.com/companies/21st
City / headquartersSan Francisco, CA, USA
source: https://www.ycombinator.com/companies/21st (Location field: San Francisco, CA, USA)
Founding year2024
source: https://www.ycombinator.com/companies/21st (Founded: 2024)
Team size3 (small team, per YC profile)
source: https://www.ycombinator.com/companies/21st (Team Size: 3)
Funding stageSeed (Y Combinator Winter 2026 batch)
source: https://www.ycombinator.com/companies/21st (Batch: Winter 2026, Status: Active)
FoundersSerafim Korablev (CEO, co-founder - previously built Rork.com, Telegram memecoin launchpad, Via cross-chain protocol backed by Naval/Safe/Sandeep) and Sergey Bunas (co-founder - ex-Deel YC W19, built Suggesty #1 Product Hunt 2022, Stage 10K users Figma competitor, Cambridge AI hackathon winner)
source: https://www.ycombinator.com/companies/21st (Founders section) cross-checked against LinkedIn search results for Serafim Korablev and Sergey Bunas
Legal entity nameNot confirmed - 21st.dev/terms and /privacy do not state a specific operating company name in the inspected content, and no Delaware/state registry hit was observed for a 21st-dev-specific entity in this run.
source: Checked curl of https://21st.dev/terms and https://21st.dev/privacy; no explicit Incorporat*/LLC/Ltd operator name observed. No state registry confirmation obtained.
Best public email on startup domainfounders@21st.dev (support@21st.dev also appears on 21st.dev/privacy and 21st.dev/terms)
source: founders@21st.dev cited in the 21st.dev Launch YC post quoted on https://www.ycombinator.com/companies/21st; support@21st.dev observed on https://21st.dev/privacy and https://21st.dev/terms via curl

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