Best 2FA & MFA APIs 2026
Which APIs actually let you issue and verify a second factor — and which 'MFA' is really an end-user app or a hardware key you can't buy as an API at all. Twilio, Duo, Auth0, and Cognito each own a real slice; Proof is the passwordless second factor that hands back a portable proof of the event.
Any of these can gate a login. Proof turns the second factor into evidence — a signed ES256 token per event, no password to phish, no app to install — at €0.0079 a check with 300 free monthly, no seat fees, no paid MFA tier. 2FA you can prove happened.
One API · One key
One key does what a stack of vendors does
Every tool on this page delivers or bundles a second factor. Proof is a single API where the factor is control of an asset — and every check returns a signed, offline-verifiable ES256 token for each of these:
Flat price · Any asset
One flat price for every asset — phone, email, and domain today, with wallet and social coming soon. No per-seat, no per-MAU, no per-verification tiers — the meter that makes every rival's bill jump.
- Free every month
- 300 proofs
- Pay as you go
- €0.03 / proof
- At volume
- €0.0079 / proof
Feature Matrix
Swipe to compare all 5 providers →
| Feature | Proof | Twilio Verify | Cisco Duo | Auth0 | Cognito |
|---|---|---|---|---|---|
| Passwordless | Yes | OTP-based | WebAuthn (paid tier) | Yes | Passkeys |
| Reverse OTP | Yes | No | Number-match (in-app) | No | No |
| MFA channels | Telegram, WhatsApp, SMS, email | SMS, voice, email, WhatsApp, push, TOTP, SNA | Push, WebAuthn, FIDO2, TOTP | SMS, voice, email, push, WebAuthn | TOTP, SMS |
| Portable proof token (offline) | ES256 JWT | No | No | OIDC only | No |
| Domain / asset verification | Yes | No | No | No | No |
| App / enrollment needed | None (channels you have) | None for SMS/email | Duo Mobile + enroll | Guardian app for push | Authenticator app for TOTP |
| No user directory required | Yes | Yes | No | No | No |
| HITL approvals for AI agents | Yes | Push only | No | CIBA (preview) | No |
| Production free tier | 300 proofs/mo | No | 10 users | 25K MAU (MFA gated) | 10K MAU |
| Pricing unit | Per-proof | Per-verification | Per-user | Per-MAU | Per-MAU |
Pricing Comparison
Swipe for pricing notes →
| Provider | Model | Price | Free Tier | Notes |
|---|---|---|---|---|
| Proof Holdings | Per-proof (any type) | From €0.0079 | 300 proofs/mo | Passwordless reverse-OTP → portable ES256 token. One price, any asset |
| Twilio Verify | Per-verification + fees | From $0.05 | None | The OTP-delivery anchor: SMS/voice/email/WhatsApp/push/TOTP/SNA. Channel fees on top |
| Cisco Duo | Per-user / month | $3–$9/user | 10 users | Workforce MFA + device trust. Passwordless/SSO need Essentials+. SMS/phone MFA retired |
| Auth0 | Per-MAU (tiered) | From $35/mo | 25K MAU | MFA is NOT free — Pro MFA from Essentials $35/mo, Adaptive MFA on Professional $240/mo. Owned by Okta |
| AWS Cognito | Per-MAU | $0.015/MAU | 10K MAU | TOTP MFA free; SMS MFA billed via SNS (~$0.006/SMS). AWS-native |
These aren't like-for-like: Proof counts verification events (proofs), Twilio charges per verification with no free tier, Duo charges per employee seat, and the identity platforms count monthly active users and gate MFA behind paid tiers (Auth0) or meter SMS (Cognito). Only Proof returns a portable proof of the 2FA event.
Category Winners
Proof Holdings
Every successful verification mints an ES256 token you can verify offline and hand to a third party — not just an in-app access decision. No other option here produces one.
Proof Holdings
The user sends a code to the service over Telegram or WhatsApp — SIM-swap-immune, no app install, no password. Proof dogfoods it for its own 2FA.
Twilio Verify
The widest set of second-factor channels behind one API — SMS, voice, email, WhatsApp, push, TOTP, and Silent Network Auth — at $0.05 per successful verification, plus channel fees.
Cisco Duo
Push, number-matched Verified Push, WebAuthn/FIDO2, and device-posture trust, now packaged as Duo IAM. The standard for protecting employee logins.
Auth0
If you already run auth on Auth0, its adaptive MFA (OTP, push, WebAuthn) rides the same platform — just budget for it, since MFA sits on the paid tiers, not the free plan.
AWS Cognito
TOTP second-factor is free and wired into IAM; you only pay SNS message fees if you add SMS MFA. Low-friction if your backend already lives on AWS.
Every asset, every channel, no passwords
Most 2FA is a code bolted onto a password. Proof Holdings starts from the other end: the factor is control of an asset, proven over a channel the person already has. A phone (over Telegram, WhatsApp, or SMS), an email (magic link or OTP), or a domain can each be the second factor — and the same Reverse OTP flow returns a signed ES256 token every time. No password to phish, no directory to breach, no app to install.
That's the spine of this category for Proof: every asset, every channel, no passwords. The same primitive does first-factor login, step-up 2FA, and asset verification — and Proof dogfoods it for its own dashboard. The other tools here are excellent at delivering or bundling a second factor; Proof is the one that turns the second factor into a portable proof you can hold.
What's not an API here
A "best 2FA API" list has to say what *isn't* buyable as an API:
- Google Authenticator and Microsoft Authenticator are end-user apps implementing the open TOTP standard (RFC 6238). There's no service to call — you generate TOTP secrets server-side with a free library and the app just works. Microsoft's Graph API manages methods *inside* Entra ID; it isn't 2FA-as-a-service.
- RSA SecurID and YubiKey are enterprise/workforce MFA — hardware tokens and FIDO2 security keys deployed by IT for staff, not a self-serve API you call to verify your customers.
- The "Authy API" no longer exists for new development: Twilio moved it to End of Support and redirects developers to Twilio Verify. The Authy consumer app lives on; the API is now Verify — which is why Authy has no row of its own here.
So a real 2FA/MFA *API* is one of two things: an OTP-delivery/verification service (Twilio Verify and its peers), or MFA bundled inside a login platform (Auth0, Cognito, and Duo for the workforce). Proof adds a third shape — passwordless asset verification with a portable proof.
Detailed Comparisons
Frequently Asked Questions
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