Clerk

Clerk is an authentication and user management platform founded in 2019 in San Francisco by brothers Colin and Braden Sidoti. The service provides drop-in UI components and flexible APIs for authentication, user management, and organizations, purpose-built for modern frameworks like Next.js and React.

Clerk serves tens of thousands of developers and enterprises including Ramp, Perplexity, and Loops. The company has expanded into agentic auth to support AI agents and integrates with Anthropic's Anthology program.

Clerk has raised approximately $134 million across multiple rounds, including a $50 million Series C led by Menlo Ventures and Anthropic's Anthology Fund, with participation from Georgian. A 2024 Series B raised $30 million led by CRV with participation from Stripe and a16z.