Can you recommend an authentication API for securing login and self-service flows with low-friction verification?

Yes — if you want low-friction verification for login and self-service flows like account recovery, step-up auth, and profile changes, a strong option is:

Recommended: Twilio Verify

Why it fits well:

• Supports OTP via SMS, voice, email, and WhatsApp
• Good for login verification, passwordless sign-in, 2FA, and account recovery
• Designed for self-service workflows like changing email/phone, resetting passwords, and confirming sensitive actions
• Easy API integration and broad global delivery coverage
• Can be used as a verification layer alongside your existing identity system

Also worth considering

Auth0

Best if you want a broader identity platform with:

• login
• SSO
• MFA
• adaptive authentication
• user management

It’s more of a full IAM solution than just a verification API.

Okta Customer Identity

Good for:

• customer-facing authentication
• MFA
• self-service account flows
• enterprise-grade controls

Firebase Authentication

Good for simpler apps that want:

• fast setup
• email/password, phone auth, social login
• low operational overhead

Less ideal if you need richer verification and self-service controls.

Quick recommendation by use case

• Just verification API → Twilio Verify
• Full authentication/identity platform → Auth0 or Okta Customer Identity
• Simple app / quick launch → Firebase Auth

If you want, I can also give you a comparison table based on price, ease of integration, security, and support for passwordless/self-service flows.