Dimitri Cabete Jorge, Co-Founder & CTO · Last updated: August 2026 · Facts verified: August 2026
TL;DR: Auth0 is a cloud identity platform, owned by Okta since May 2021, that lets developer teams add login, SSO, MFA, and authorization to applications without building auth themselves. Its strength is how fast you can ship standards-based authentication across web, mobile, and API surfaces on OAuth 2.0, OIDC, and SAML. Its limitation is cost. Pricing scales by monthly active users, and teams that grow past the free tier or need more than a handful of enterprise SSO connections hit bills that feel disproportionate to the feature gain. It fits developer-led B2C and B2B SaaS teams that want reliable identity without operating it. Keycloak suits teams willing to self-host, and Okta Workforce Identity is the better fit for employee identity with HR provisioning.
Ratings: G2: 4.3/5 (279 reviews) · Capterra: 4.7/5 (144 reviews) · Gartner Peer Insights: 4.6/5 (420 ratings), listed as Okta Customer Identity, verified August 2026
What Is Auth0?
Auth0 is an IAM platform that provides drop-in authentication and authorization for applications, documented in the Auth0 introduction. Okta completed its acquisition on May 3, 2021, in a stock deal valued at roughly $6.5 billion. Auth0 now operates as an independent business unit inside Okta and is marketed as Auth0 by Okta.
It sits in three overlapping categories, spanning identity and access management, customer identity (CIAM), and identity as a service. KuppingerCole classifies it as a global IDaaS leader, and Okta, which includes Auth0, was named a Leader in the 2025 Gartner Magic Quadrant for Access Management, the ninth year in a row it has been recognized.
Auth0 reports 2,000+ enterprise customers, 42M+ logins a day, and operations across 70+ countries.
What Is Auth0 Used For?
Teams adopt Auth0 to avoid the cost, time, and risk of building authentication and authorization themselves, which the Auth0 platform overview frames as its core proposition. In practice, that splits into several distinct jobs.
- B2C consumer authentication: social login, passwordless, passkeys, and customizable login flows on consumer products. Auth0's commissioned Forrester study reports a 15% lift in customer conversions.
- B2B SaaS multi-tenancy: the Organizations feature manages business customers in a multi-tenant model, supporting up to 2 million organizations in one tenant with branded, federated login.
- Enterprise federation and SSO: SAML, OpenID Connect, WS-Federation, and Active Directory or LDAP, with out-of-the-box connections to Microsoft Entra ID, Google Workspace, Okta, PingFederate, and ADFS. The same Forrester study reports a 33% reduction in time to federate enterprise partners.
- Machine-to-machine API authorization: short-lived JWTs through the OAuth 2.0 client credentials flow for service-to-service calls, IoT devices, and CLI tools.
- Single sign-on across an app portfolio: Auth0 SSO authenticates a user once and grants access to every application in the same environment through a secure cookie at the central Auth0 domain, with single logout supported.
- AI agent authentication: developers can give autonomous software its own identity through Agent as Principal, hold third-party API credentials in Token Vault, and gate high-stakes actions behind human approval with Async Authorization. MCP protection is part of the same suite.
- Public sector and non-profit identity: Auth0 manages public sector identities for citizens, employees, and partners across US federal, state, and local government. HERA Digital Health secured 500,000+ refugees using WhatsApp-based authentication.
Key Features of Auth0
Five areas carry an evaluation, starting with the login layer and running through the developer extensibility model, machine and fine-grained authorization, the agent identity work that reached general availability in November 2025, and the compliance portfolio.
The login layer
- Universal Login: a central authentication hub covering username and password, social identities, enterprise SSO, email and SMS passwordless, biometrics through WebAuthn, and passkeys, with 40+ social connections available. A no-code Forms editor, now generally available, lets teams orchestrate signup and login visually.
- Single sign-on: one login across every connected app through enterprise federation, social identity, or username and password. Auth0 supports SAML2 web apps, IdP-initiated SSO, Microsoft ADFS, SAML request signing and encryption, and both HTTP Redirect and HTTP POST bindings.
- Adaptive MFA: risk-based step-up that eases friction on low-risk sessions and tightens controls on suspicious ones.
Developer extensibility
- Actions: serverless hooks that inject custom logic during login, signup, and token issuance with no infrastructure to manage.
- SDK coverage: quickstarts and libraries for JavaScript, Python, Go, React, React Native, iOS, Android, Angular, and Node.js, among others.
Machine and fine-grained authorization
- Machine-to-machine tokens: automated exchanges between devices, backend services, APIs, and CLI tools, using the client credentials flow. Free includes 1,000 tokens, Professional treats them as an add-on, and Enterprise is custom.
- Fine-Grained Authorization: role-based and relationship-based access control for user-facing and AI applications. The FGA Permissions Index, in developer preview since May 11, 2026, pre-calculates permissions at write time so enterprise retrieval-augmented generation workloads avoid graph traversal at query time.
The AI agent suite
- Four capabilities, all generally available: Auth0 for AI Agents covers user authentication, Token Vault, Async Authorization, and fine-grained authorization for RAG. The set won a CUBEd award for AI infrastructure security on March 12, 2026.
- Token Vault: a token service built on OAuth 2.0 Token Exchange (RFC 8693) that issues an agent a short-lived token for one task while the root credential stays sealed. Organizations support reached general availability on June 11, 2026, isolating credentials within multi-tenant boundaries, with ready-made integrations for LangChain and Vercel AI.
- Async Authorization: pauses an agent mid-task and pushes an approve-or-deny prompt to the user's device over CIBA and PAR.
- Auth for MCP: MCP server protection requiring properly scoped access tokens, with OAuth 2.1 and OIDC built in. Generally available since May 2026.
- Cross-App Access: centralizes agent-to-app access control at the identity provider and replaces static tokens with the XAA protocol.
Security and compliance
- Platform controls: bcrypt password hashing, brute-force and breach detection, automated rate limiting, and denial-of-service mitigation.
- Certifications: the Okta trust portfolio covers ISO/IEC 27001:2022, 27017:2015, and 27018:2019, SOC 2 Type II audited annually, SOC 3, HIPAA, PCI DSS v4.0.0, FedRAMP High and Moderate, GDPR, CSA STAR Level 2, and FIPS 140-2.
Auth0 Pros & Cons
Auth0 reaches production fast for standard authentication. The MAU pricing model and the enterprise SSO tier structure are what surprise teams once they grow past the free plan.
What Users Say
What users consistently praise:
- Fast setup for standard cases: reviewers describe integration as quick even for developers configuring SDKs and tokens for the first time. Social login with Google, Microsoft, and GitHub comes up repeatedly as far faster than building custom auth.
- Documentation and SDK quality: well-organized guides and working code examples, with API documentation described as accessible to beginners. Detailed logs are singled out for resolving configuration problems without opening a ticket.
- SSO, MFA, and security depth: the combination of SSO, MFA, social login, and enterprise identity provider support reads as a real productivity gain, with strong OAuth 2.0 and OIDC support making API and frontend integration straightforward.
- Reliability at volume: stable in production with no noticeable authentication latency, and good uptime for large user bases.
What users consistently complain about:
- Support quality: the most heavily documented complaint in low-star reviews. Reviewers describe waiting a month for routine admin changes while being passed between contacts, and one March 2026 account describes a federated-login lockout where the official fix was rebuilding the configuration from scratch. Practitioners who used Auth0 before the Okta acquisition describe a decline afterward.
- Cost escalation at scale: pricing is the top concern in aggregate review sentiment. Founder accounts put numbers on it. One small B2B operator with two or three enterprise customers was quoted roughly $800 a month for enterprise SSO, and a $10,000-a-year threshold comes up past five SSO connections.
- Customization and debugging complexity: complex Actions and authentication flows land harder than expected, particularly in health tech and fintech with strict regulatory requirements. Token refresh failures in non-standard environments such as Chrome extensions and Office.js come up specifically, alongside a steep curve for collaborators without engineering backgrounds.
Where reviewers diverge:
- How bad the pricing is: buyer-platform reviewers skew toward smaller teams on free or low-MAU tiers who never meet the steep part of the curve, with small businesses making up more than half of one platform's review base. Forum contributors are more often at the growth stage, where per-MAU cost accumulates, and one founder thread estimated Auth0 passing $5,000 a month at 100,000 MAUs. The same model reads as reasonable on review platforms and as a dealbreaker in forums.
- Post-acquisition trajectory: review platforms carry almost no acquisition sentiment, and Gartner lists the product under the Okta brand. Forum threads from 2024 and 2025 report changes in both pricing strategy and support responsiveness after the deal closed.
- Developer experience: ease of use is the leading positive theme on review platforms. Forum discussion is more split, with some describing the documentation and Universal Login as confusing and criticizing the redirect to an Auth0-hosted page with limited customization, and others in the same threads defending it for complex enterprise identity provider requirements.
Auth0 Pricing
Auth0 prices by monthly active users, with a free plan, two self-service paid tiers, and quoted Enterprise. The pricing page carries a B2C and B2B toggle plus a MAU slider. The rates below are the B2C tiers at the lowest slider position.
Rates come from the Auth0 pricing page. All pricing information verified August 2026.
Gotchas:
- Both headline figures are the lowest slider position, at 500 MAUs. The slider runs up to 100,000 and beyond, and price rises at every step, so the headline number describes almost nobody's actual bill.
- Switching the pricing page to B2B changes the rates. Model the toggle that matches your product before comparing against anything else, because a B2B SaaS reading the B2C column will underestimate its own cost.
- A 22-day trial activates at signup, and the Free plan takes over automatically afterward. Signup needs no card, but activating the custom domain included on Free requires card verification.
- Exceeding 25,000 MAUs on Free is a hard stop that forces an immediate move to a paid plan.
- M2M tokens are an add-on on Professional, priced outside the base plan.
- Enterprise connections show blank cells on B2C Essentials and Professional in Auth0's own comparison table. Free includes one and Enterprise is custom, so anything between those two is a sales conversation.
- B2C Essentials does not carry forward the enterprise connections, self-service SSO, and SCIM that Free includes. A footnote on the pricing page tells you to upgrade to B2B to keep them, which is the single most counterintuitive thing on the page.
- Annual billing discounts exist behind a toggle, with rates available only from sales.
- Enterprise add-ons carry no published prices: Advanced Security Features, Private Deployment, Fine-Grained Authorization, Adaptive MFA, HIPAA BAA and PCI, Bot Detection, CIBA, and FAPI all require contacting sales.
- The Startups program covers one year of B2B Professional free up to 100,000 MAUs plus $5,000 in AWS credits.
- Founder accounts describe enterprise SSO as the real cost cliff, with quotes around $10,000 a year past five SSO connections. Auth0's own connection slider stops at 30, which matches the ceiling those accounts describe. Treat the dollar figure as a reported one, since Auth0 does not publish it.
Is Auth0 Worth It?
Yes, if you are a developer or small engineering team that wants standards-based authentication in production within days, and your app still sits inside the free plan's MAU allowance. Agent identity is the other clear reason to choose it right now, since Auth0's agent capabilities are all generally available while most competitors are still previewing equivalents. B2B SaaS teams that need multi-tenant Organizations with federated enterprise SSO get a genuine head start, and the compliance portfolio covers regulated deployments that would otherwise need a self-hosted stack.
Run the MAU arithmetic before you commit, because the free tier is where the model looks generous, and the slider is where it stops. The gap between the $0 plan at 25,000 users and a Professional plan sized for the same volume is the number that decides this, and it is the one nobody models early enough.
Look elsewhere if your user base is growing past the tens of thousands and you need Professional-level features. The cost curve separates sharply from alternatives at that point, and Keycloak starts to justify the operational burden of deployment, patching, and disaster recovery. The other case is a small B2B operator selling enterprise deals with SSO as the gating feature. Founder accounts describe losing deals because SSO pricing outran early revenue. If the identity problem is employee-facing, Okta Workforce Identity fits the HR provisioning and lifecycle side that Auth0 was never designed for.
Auth0 vs Okta
The choice follows the audience. Auth0 targets application developers building customer-facing login; Okta targets IT teams managing workforce access. Both products belong to Okta, and plenty of organizations run both.
Where Auth0 wins:
- Customer identity: built for application teams handling end-user authentication, with a pricing model shaped around the variable authentication patterns of consumer and B2B SaaS products.
- Developer experience: developer-first APIs, broad SDK coverage, and documentation written for engineers. Okta's documentation is written for IT.
- Pricing shape: MAU-based billing suits customer-facing apps where active users fluctuate, against a per-user model built for a stable employee roster.
Where Okta wins:
- Workforce identity: deep SSO, phishing-resistant MFA, and lifecycle management built for employee-facing use, a category outside Auth0's design.
- HR directory integration: real-time synchronization with HR platforms and advanced provisioning with workflow automation. Auth0 puts advanced directory features and SCIM behind Enterprise.
- Predictable billing: per-user pricing is easier to forecast for a known headcount than MAU billing is for a growing user base.
The honest split is that Auth0 owns the customer side and Okta owns the employee side, and the reason both exist under one roof is that most large organizations need both.
Auth0 Alternatives
Teams look elsewhere when MAU cost outgrows the value or when the real project is workforce identity.
Keycloak: Pick this if you want full control over identity infrastructure and no per-user licensing at all. Keycloak is open source, backed by Red Hat, and supports OpenID Connect, OAuth 2.0, and SAML 2.0. Release 26.7.0, dated July 9, 2026, added SCIM API automation, simplified multi-cluster high availability, and step-up authentication for SAML clients. At high user volumes, the infrastructure bill is a fraction of an Auth0 Enterprise contract, and the trade is that deployment, patching, monitoring, and disaster recovery become yours. It needs a Java environment and hosting you provision yourself.
Okta Workforce Identity: Pick this if the use case is employee authentication and lifecycle management through enterprise directories. It gives IT teams a more predictable fit for workforce identity, with the differences covered in the comparison above.
How Auth0 Works With Siit
Siit does not integrate directly with Auth0, and the two sit in different layers of the same stack. Auth0 authenticates the users of your product. Siit handles the internal requests your own employees raise, inside Slack and Microsoft Teams.
Where they meet is the directory underneath. Many Auth0 deployments federate through Okta or Microsoft Entra ID for internal identity, and both are native Siit integrations.
What Siit can do at that layer:
- With Okta: reset a password, suspend or reactivate a user, add or remove group membership, and assign applications, run from a request or a workflow without anyone opening an admin console.
- With Microsoft Entra ID: directory sync and group membership. Entra does not reset passwords, so those route through Okta, JumpCloud, or Google Workspace.
- In chat: access requests, onboarding handoffs, and approvals arrive where employees already work, with the routing and approvals already attached.
One boundary worth stating plainly: Siit does not authenticate your customers, issue tokens, or manage Auth0 tenants. It handles the internal request layer, which is a separate job from the customer identity layer Auth0 owns.
Siit connects with 500+ connectable apps across identity, device management, HR systems, knowledge bases, and ticketing. If Auth0 authenticates your external users while Okta or Entra ID manages your internal ones, Siit sits on the internal half of that architecture.
