Clerk

Clerk is a complete authentication and user management platform built for modern web and mobile applications. It provides drop-in UI components for sign-up, sign-in, user profiles, organization management, and billing that can be deployed to a custom domain and styled to match any brand. Clerk handles the full spectrum of auth complexity including multifactor authentication, social sign-on (20+ providers), magic links, passkeys, session management, fraud detection, and bot prevention. For B2B SaaS applications, Clerk offers multi-tenancy with custom roles and permissions, organization switching, auto-join by email domain, and invitation flows. The platform integrates natively with Next.js, React, Expo, Astro, and major backends including Supabase and Vercel.