Best Authentication APIs 2026
Seven ways to handle auth. Six are full identity platforms that log users in and own the user directory — Auth0, Okta, Stytch, Descope, Firebase, Cognito. The seventh, Proof, is a passwordless login-and-verification primitive: prove control of an asset, get back a portable token, no directory at all. Pricing from each vendor's own pages, July 2026.
If you need to run identity, pick one of the six on their merits. If you need to verify and log people in without owning a directory — passwordless, per-proof, a portable token at the end — Proof is the only one shaped like that, and it composes with all six.
One API · One key
One key does what a stack of vendors does
Every platform on this page wants to run your user directory. Proof is a single API you call from your own stack — the same reverse-OTP flow issues 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 7 providers →
| Feature | Proof | Auth0 | Okta | Stytch | Descope | Firebase | Cognito |
|---|---|---|---|---|---|---|---|
| Passwordless | Yes | Yes | Yes | Yes | Yes | Yes | Yes |
| MFA / 2FA | Reverse OTP | Yes | Yes | Yes | Yes | Identity Platform | Yes |
| SSO / SAML / OIDC | No | Yes | Yes | Yes | Yes | Identity Platform | Yes |
| Domain verification | Yes | No | No | No | No | No | No |
| Wallet verification | Coming soon | No | No | Yes | No | No | No |
| Reverse OTP | Yes | No | No | No | No | No | No |
| Portable proof token (offline) | Yes | OIDC only | No | No | No | No | No |
| HITL approvals for AI agents | Yes | CIBA (preview) | No | No | No | No | No |
| User directory / sessions | No | Yes | Yes | Yes | Yes | Yes | Yes |
| Production free tier | 300 proofs/mo | 25K MAU | No | 10K MAU | 7.5K MAU | 50K MAU | 10K MAU |
| Pricing unit | Per-proof | Per-MAU | Per-user/MAU | Per-MAU | Per-MAU | 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 | One price for phone, email, domain (wallet + social coming soon) |
| Firebase Auth | Free classic / per-MAU | Free · $0.0055/MAU | 50K MAU (IP) | Basic auth free; MFA/SAML need the Identity Platform upgrade. GCP lock-in |
| AWS Cognito | Per-MAU | $0.015/MAU (Essentials) | 10K MAU | Free tier cut from 50K in Dec 2024. AWS-native federation. Plus tier: no free |
| Stytch | Usage-based per-MAU | From ~5¢/MAU | 10K MAU | No feature gates (MFA/SSO/RBAC on free). Owned by Twilio (2025) |
| Auth0 | Per-MAU (tiered) | From $35/mo | 25K MAU | 25K free tier is feature-limited (basic MFA, limited SSO). ~$0.07/MAU effective (B2C Essentials). Owned by Okta |
| Descope | Flat tiers + per-MAU | $249-799/mo | 7.5K MAU | Billed annually (3 SSO / 10 tenants on free). No-code Flows. $0.05/MAU overage |
| Okta | Per-user / per-MAU | From $6/user/mo | None (prod) | Annual only, $1,500 min. Enterprise SSO + governance. Advanced tiers contact-sales |
Free tiers here aren't like-for-like: the six identity platforms count monthly active users (MAU), and Auth0, Firebase, and Cognito gate MFA, SSO/SAML, or multi-tenancy behind paid upgrades. Proof's 300 counts verification events — any asset type, no feature gates — so the free-tier column is measuring two different things.
Category Winners
Proof Holdings
The only one that verifies domain control and returns a portable proof token — no user directory required. Per-proof, €0.0079 on Business.
Auth0
Best-in-class SDK and quickstart breadth, clean docs, Actions extensibility, B2B Organizations, and a generous 25K-MAU free tier.
Okta
7,000+ app integrations (OIN), identity governance, phishing-resistant MFA, and the compliance depth large regulated orgs need.
Descope
Descope Flows — a drag-and-drop editor to build and change auth journeys without redeploying. Genuinely differentiated.
Stytch
MFA, SSO, RBAC, and SCIM all work on the 10K-MAU free tier — nothing paywalled; usage-based per-MAU beyond (rate via its calculator).
Firebase Auth
Classic Firebase Authentication is free with no MAU ceiling for email and social sign-in — unbeatable for a Google-Cloud app that only needs basic login (phone auth still bills per SMS).
AWS Cognito
SAML/OIDC federation into IAM roles and API Gateway authorizers, with identity inside your existing AWS account, billing, and compliance boundary. Low-friction if your backend already lives on AWS.
Proof Holdings
ES256 attestations verifiable offline by anyone. Auth0 has OIDC tokens, but they're session-bound to the issuing app.
Proof Holdings
Approvals delivered via Telegram/WhatsApp with a signed proof token — no app install. Auth0's CIBA is a Developer Preview requiring its Guardian app.
Six identity platforms and one verification layer
Auth0, Okta, Stytch, Descope, Firebase, and Cognito are identity platforms: they log users in, keep a user directory, manage sessions, and bill per monthly active user (or per seat). They differ on developer experience, enterprise depth, and price — but they're the same category, and you pick one to be your app's front door.
Proof Holdings is a different shape. It doesn't run a user directory, sessions, or SSO — but you can still use it to log people in, the passwordless way: a user proves control of a specific asset (a phone, an email, a domain — wallet and social coming soon) and you get a portable ES256 token you can verify offline. No password to store, no account required — Proof dogfoods exactly this for its own login and 2FA. It's the verification-and-login primitive you call *from* your stack, including for people who will never have a stored account with you.
So the real question isn't "which auth API is best?" — it's "do you need to *run* a full identity system, or to authenticate and verify control of an asset?" If you need a user directory, sessions, SSO, and governance, pick from the six on their merits. If you want passwordless, account-less login, domain verification, portable proofs, human approvals, or per-verification pricing — that's Proof, and it composes with any of them.
Detailed Comparisons
Frequently Asked Questions
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