Auth0
Enterprise-grade auth that handles every login method — from social login to SAML SSO
Free up to 7k MAU, from $23/mo
Clerk
Drop-in auth with pre-built UI components — sign-up, sign-in, and user management in minutes
Free up to 10k MAU, from $25/mo
Firebase Auth
Google's authentication service with generous free limits and tight integration across the Firebase ecosystem
Free up to 50k MAU (phone auth: 10k/mo free)
Lucia
Lightweight open-source auth library that gives you full control over your authentication logic
Free and open source
Memberstack
Add memberships and payments to any website
From $25/mo
Stytch
Passwordless authentication API focused on magic links, OTPs, and passkeys
Free up to 25 orgs or 1k MAU, from $99/mo
SuperTokens
Open-source authentication you can self-host for free or use their managed service
Free self-hosted, managed from $0 (up to 5k MAU)