Permit.io

Seamless Integration of SSO, MFA, passwordless auth and more. Includes SDKs for frontend and backend apps. Free up to 1000 MAUs and five identity providers.

Open source user authentication that natively integrates into your app - enabling you to get started quickly while controlling the user and developer experience. Free for up to 5000 MAUs.

Enterprise SSO (SAML, OIDC), SCIM provisioning, and social logins for B2B SaaS. Free tier includes 1 million MAU, 100 organizations, 1 SSO connection, and 1 SCIM connection.

A Sell to companies of any size immediately with a few lines of code, free up to 200 users and 10k Transactional Emails (with a watermark branding: "Powered by PropelAuth").

Keycloak Open Source Identity and Access Management. Free realm up to 1000 users, up to 10 SSO connections, leveraging Phase Two's Keycloak enhanced container which includes the Organization extension.

MojoAuth makes it easy to implement Passwordless authentication on your web, mobile, or any application in minutes.

Keycloak Identity and Access Management as a Service. Free up to 100 users and one realm.

Two-factor authentication (2FA) on multiple devices, with backups. Drop-in replacement for Google Authenticator. Free for up to 100 successful authentications.