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21st
AddedJun 25, 2026
UpdatedJul 2, 2026
21st

21st

Seed

Infrastructure and UI building blocks for the agentic internet.

HQ
San Francisco, CA, US
Accelerator
Y Combinator logoY CombinatorW26
Overview
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Fundraising
Employees
Website

21st.dev is the largest React component registry for AI applications, used by 2M developers (370K MAU).

21st provides a product described as infrastructure and UI building blocks for the agentic internet.

21st - Similar Companies

Emergent logo

Emergent

emergent.sh

HeroUI logo

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heroui.com

x1 logo

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assistant-ui logo

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Variant logo

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ProjectX logo

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Syntropy logo

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Terminal Use logo

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primitive logo

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The Company Company logo

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Superset logo

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vly.ai logo

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A1Zap by A1Base logo

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21st - Quick Facts

Who are 21st's competitors?

Companies similar to 21st include Emergent, HeroUI, x1 and assistant-ui.

Where is 21st's headquarters located?

21st's headquarters is located in San Francisco, CA, US.

When was 21st's last funding round?

21st's most recent funding round was for $500k (USD) in January 2026.

How much has 21st raised to-date?

As of Jan 1, 2026, 21st has raised a total of $500k (USD).