Keycloak
keycloak.orgAuthentication
The free, self-hosted IAM workhorse everyone reaches for when procurement won't approve a SaaS auth bill.
Other products from Authentication
The battle-tested default for customer identity; heavier and pricier than newer options, but nobody gets fired for picking it.
Bolt on enterprise SSO, SCIM, and directory sync only when a big customer demands it, without rearchitecting your existing auth.
Own your user table instead of renting it — a framework-agnostic TypeScript auth library that's fast becoming the default for new projects.
Open-source and self-hostable if you want Auth0-grade features without an Auth0-grade bill or vendor lock-in.