Clerk
Clerk is an Authentication & Passwordless company founded in 2019 and based in San Francisco, United States. It has raised $134M in total funding, most recently a Series C in 2025.
Founded in 2019 by brothers Colin Sidoti (CEO) and Braden Sidoti, Clerk provides a complete, drop-in authentication and user-management solution built around prebuilt UI components for React, Next.js, and other modern frameworks. Instead of assembling sign-in, sign-up, session, and profile flows by hand, developers embed Clerk's components and get passwordless, social, multi-factor, and organization-based auth out of the box. The company reported reaching millions of users on the platform, and in June 2025 raised a $50M Series C led by Menlo Ventures, with participation through the Anthology Fund (a partnership between Menlo and Anthropic) and Georgian, as it expanded into identity for AI agents.
Clerk turned authentication into a set of polished frontend components, making it a default choice in the React and Next.js ecosystem and an early mover on agent identity.
clerk.com ↗·Authentication & Passwordless·
United States·private 
