The best authentication & identity tools in 2026

Across the reviewed leaders, Firebase and Appwrite pair authentication with broader backend building blocks like databases, realtime sync, storage, and serverless functions for teams shipping apps quickly. Clerk stands out for polished drop-in sign-in, session handling, and organization-aware user management, while the wider field also emphasizes enterprise SSO, passwordless flows, MFA, and granular authorization for B2B products.