Identity platform with authentication, authorization, and user management for web, mobile, and API applications. Free up to 25,000 MAUs, paid plans from $35/month.
Handles user login and security for your apps — supports passwords, social logins, and enterprise single sign-on out of the box.
Auth0 is the authentication layer you bolt on so you never have to think about password hashing, token rotation, or SAML integration again.
Building authentication from scratch takes a security-focused team 3-6 months to get right. One mistake in session management or password storage creates a breach. Auth0 replaces that risk with a single integration that handles login flows, MFA, SSO, and user management across every identity protocol your enterprise customers will demand (SAML, OAuth 2.0, OpenID Connect, WS-Federation).
Auth0's Universal Login provides a single, customizable login page that works across web, mobile, and API applications. You design it once; Auth0 handles the security plumbing behind it. The Actions engine lets you inject custom JavaScript at any point in the authentication flow (post-login, pre-registration, post-password-change), giving you flexibility without touching the core auth infrastructure.
The Organizations feature handles multi-tenant B2B SaaS applications. Each customer gets their own login experience, SSO configuration, and member management, without you building tenant isolation from scratch. For SaaS builders selling to enterprises, this feature alone saves months of development.
Passkeys support (added in 2025-2026) enables phishing-resistant authentication using biometrics and hardware keys. This is where the industry is heading, and Auth0 adopted it before most competitors outside of Okta (which owns Auth0, making the relationship more like sibling products).
Source: auth0.com/pricing
The free plan's 25,000 MAU limit is generous for development and early-stage apps. But the paid tiers start at just 500 MAUs, so a growing app with 5,000 active users needs to negotiate pricing. Clerk starts at $25/month for 10,000 MAUs, and WorkOS offers a free tier for SSO connections. Auth0's value shows at enterprise scale where the breadth of protocol support and compliance certifications (SOC 2, HIPAA, PCI DSS) justify the premium.
On Reddit's r/node, developers praise Auth0 for reducing complex authentication to "one click" integrations, noting it handles edge cases (token refresh, session management, MFA enrollment) that take months to build correctly.
The primary complaint across Reddit threads in r/reactjs and r/node is cost at scale. Startups generating less than $500K/month in revenue find Auth0 pricing hard to justify, with multiple developers recommending Clerk or self-hosted alternatives for cost-sensitive projects. The learning curve for advanced features (Actions, custom database connections, Organizations) draws criticism from developers unfamiliar with identity protocols.
Sources: aretheadvantagesofusingthirdparty/" class="text-blue-700 dark:text-blue-300 underline decoration-current underline-offset-2 hover:no-underline" target="_blank" rel="noopener noreferrer">Reddit r/node, yourecommendbuildingyour_own/" class="text-blue-700 dark:text-blue-300 underline decoration-current underline-offset-2 hover:no-underline" target="_blank" rel="noopener noreferrer">Reddit r/reactjs
Passkeys support for phishing-resistant biometric and hardware key authentication. Enhanced Organizations for multi-tenant B2B SaaS. Positioning as a full CIAM platform with deeper customization for enterprise use cases.
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Auth0 remains the default choice for teams that need production-grade authentication without building it from scratch. The 25,000 MAU free tier is the best in the identity space, and the protocol breadth (SAML, OAuth, OpenID Connect) handles any enterprise requirement. The pricing jump from free to paid is steep for mid-stage startups, and vendor lock-in is real if you store credentials in Auth0's database.
Centralized login experience hosted by Auth0 that handles authentication flows, password resets, and MFA while maintaining your brand identity
Use Case:
Implement secure login for a multi-tenant SaaS application where users authenticate once and access multiple sub-applications with SSO
Server-side JavaScript functions that execute during authentication to add custom business logic, enrich user profiles, or integrate with external systems
Use Case:
Automatically assign user roles based on email domain during signup and send new user notifications to Slack via webhook
Pre-configured integrations with enterprise identity providers like Active Directory, Azure AD, LDAP, and SAML-based systems
Use Case:
Enable enterprise customers to use their existing Active Directory for SSO while maintaining separate user databases for other customer types
Adaptive MFA with support for SMS, email, authenticator apps, hardware tokens, and biometrics with risk-based triggering
Use Case:
Require MFA for admin users always, but trigger it for regular users only when logging in from new devices or suspicious locations
Multi-tenant user management that allows users to belong to multiple organizations with different roles and permissions
Use Case:
Build a B2B platform where users can be members of multiple companies with different access levels in each organization
Client credentials flow for API authentication with scope-based permissions and token management for server-to-server communication
Use Case:
Secure microservice communication where each service authenticates with Auth0 to access other internal APIs with specific scopes
Free
month
$35.00/month
month
$240.00/month
month
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View Pricing Options →Enterprise SaaS applications requiring robust authentication and compliance certifications
B2B platforms with multiple organizations needing tenant isolation and SSO
Regulated industry applications requiring HIPAA, PCI DSS, or SOC 2 compliance
API-first applications needing machine-to-machine authentication and authorization
Applications requiring complex user management with custom business logic during authentication
Auth0 works with these platforms and services:
We believe in transparent reviews. Here's what Auth0 doesn't handle well:
Auth0 charges based on Monthly Active Users (MAUs) - users who log in at least once per month. The Essential plan starts at $23/month for 1,000 MAUs, then $0.05 per additional MAU. B2C features like social logins are included, but B2B features like SAML connections cost extra. If you have 50,000 registered users but only 10,000 log in monthly, you pay for 10,000 MAUs, not 50,000 total users.
Yes, through Custom Database Connections, you can keep user data in your existing database while using Auth0 for authentication. Auth0 provides scripts to authenticate users, create accounts, verify emails, and reset passwords against your database. You can migrate users gradually - Auth0 authenticates against your database first, then imports users to Auth0's database upon successful login, eventually deprecating the legacy database.
Rules are the legacy system using Node.js 8 with limited npm modules, while Actions are the modern replacement using Node.js 18+ with full npm support and better debugging tools. Actions provide versioning, better error handling, and integration with Auth0's dashboard for testing. New implementations should use Actions, and Auth0 provides migration tools to convert existing Rules to Actions with minimal code changes.
Auth0 provides built-in GDPR compliance tools including user data export APIs, right-to-be-forgotten deletion workflows, and data processing agreements. User data can be stored in EU regions (Frankfurt) to meet data residency requirements. The platform includes audit logs for data access, user consent management for tracking consent preferences, and automatic PII detection in logs to prevent accidental exposure of sensitive data.
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Passkeys for phishing-resistant authentication. Enhanced Organizations for multi-tenant B2B SaaS. Full CIAM platform positioning with deeper enterprise customization.
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