Clerk

Clerk provides a complete authentication and user management solution that lets development teams integrate full login systems without building them from scratch, and includes an MCP server as part of its feature set. Ready-to-use UI components cover sign-up, sign-in, and profile management for web and mobile applications.

Authentication features include multi-factor authentication, social sign-on, magic links, traditional passwords, and bot detection and fraud prevention. For multi-tenant applications, Clerk offers organization management with custom roles, invitations, and auto-join; built-in billing also lets teams manage subscriptions, plan configuration, and content gating directly through the same platform instead of integrating a separate billing solution. SDKs are available for Next.js, React, Expo, Astro, React Router, and TanStack React Start, among others.

The business model is freemium: the first 50,000 monthly active users and 100 organizations per month are free, with no credit card required; usage-based paid tiers apply above that.

Clerk's referenced customers include Vercel, Supabase, Inngest, and Upstash — notably, several of them developer tools themselves, suggesting particularly strong adoption within the developer community.

Clerk raised a $30 million funding round in 2024 and struck a strategic partnership with Stripe that same year to tie payment processing more closely to user management — a sign of the growing trend toward treating authentication and billing as a shared infrastructure layer rather than separate systems.