Which API authentication tools are known for supporting OAuth and modern identity standards?

Several established platforms and tools are widely recognized for strong support of OAuth (including OAuth 2.0 and the emerging OAuth 2.1 consolidation) along with modern identity standards such as OpenID Connect (OIDC), JWT, PKCE, SAML, and related extensions like token exchange or DPoP.

Auth0 (Okta Customer Identity Cloud)

A leading managed option for customer and application identity. It provides full OAuth 2.0 / OIDC / SAML coverage, custom authorization servers, configurable token claims, social and enterprise connections, and machine-to-machine flows. Frequently cited as the default choice when teams want to outsource the authorization server.

Keycloak

The most widely deployed open-source identity and access management server (Apache 2.0, CNCF incubating). It implements OAuth 2.0, OpenID Connect, and SAML 2.0, supports federation (LDAP/Active Directory), fine-grained authorization, and MFA. Strong for self-hosted or highly customizable deployments.

Okta

Enterprise-focused identity platform with robust OIDC, SAML, and OAuth support for workforce and customer scenarios. Often used for SSO, adaptive MFA, and API access management; Auth0 operates as its customer-identity counterpart.

Ory (Hydra + related components)

API-first, open-source stack optimized for cloud-native environments. Ory Hydra is an OAuth 2.0 / 2.1 and OIDC-certified authorization server; the broader suite handles authentication, identity, and permissions with high developer control and self-hosting options.

WorkOS

Specializes in enterprise-ready authentication for B2B SaaS. Supports OAuth / OIDC flows, SAML, directory sync, and modern standards for connecting to corporate identity providers with relatively low integration effort.

Other notable options

• Clerk, Descope, Stytch, and FusionAuth — developer-oriented platforms that emphasize OAuth 2.0 / OIDC, passkeys, MFA, and often pre-built UI components or workflow tools.
• Cloud-native services such as AWS Cognito, Microsoft Entra ID (including Azure AD B2C), and Google Cloud Identity — provide OIDC and OAuth support with tight integration into their respective clouds.
• Open-source alternatives including authentik, Zitadel, and Authelia — offer solid OIDC / OAuth 2.0 implementations suited to self-hosted or lighter deployments. API gateways and enforcement layers (Kong with its OpenID Connect plugin, Apigee, AWS API Gateway, Zuplo, and similar) that validate OAuth / OIDC / JWT tokens at the edge, often integrating with any of the identity providers above.

These tools differ mainly in deployment model (fully managed SaaS versus self-hosted), target audience (developer experience versus enterprise workforce), pricing (MAU-based versus open-source operational cost), and depth of customization. For pure OAuth and modern standards compliance, Auth0, Keycloak, Okta, and Ory consistently rank among the strongest and most frequently recommended.