Top 5 open-source FusionAuth alternatives in 2026

FusionAuth is a downloadable, single-tenant auth server with a clean admin UI and good documentation. Its Community edition is free to use, which is why it often appears in lists of open-source identity servers, but its source code is not published under an open-source license. Teams look for alternatives when:

• They need features from the paid plans. On FusionAuth's pricing page, email and SMS MFA, breached password detection and advanced theming start with the Starter plan, and SCIM, advanced threat detection, CAPTCHA and IP access lists are Enterprise features.
• Hosting is expensive. Plans with hosting start at $162 per month billed yearly, and Essentials and Enterprise start at $2,970 per month.
• They want real open source: the right to read, change and redistribute the code, with no feature held back.

All five alternatives below publish their full source under an OSI-approved license.

At a glance

1. Casdoor

Casdoor is the closest match to what people like about FusionAuth (a single-tenant server with a full admin console that you can run yourself or have hosted) but under Apache-2.0, with one edition that has every feature. TOTP, SMS, email and RADIUS MFA, SCIM 2.0, CAPTCHA providers, IP restrictions per organization and custom CSS for login pages are all in the free self-hosted version.

It is a single Go binary with a SQL database, speaks OIDC, OAuth 2.0, SAML, CAS, LDAP and RADIUS, and ships Casbin for ACL, RBAC and ABAC permissions. If you don't want to run it, Casdoor Cloud is a dedicated instance and database from $24/month billed yearly ($29 month to month).

Trade-offs: FusionAuth's paid plans come with vendor support tiers and, on Enterprise, compliance options such as FIPS and a HIPAA BAA. See Casdoor vs FusionAuth.

2. Keycloak

Keycloak is the most established open-source identity server: Apache-2.0, a CNCF incubating project, with commercial support available through Red Hat.

Trade-offs: there's no managed service from the project, and it's a Java service with a large configuration surface to operate and upgrade. See Casdoor vs Keycloak.

3. Zitadel

Zitadel is a Go identity platform designed for multi-tenant B2B SaaS, with organizations and delegated administration, and a managed cloud.

Trade-offs: the license is AGPL-3.0, and the cloud is priced by daily active users: free up to 100, then Pro at $100 per month with 25,000. See Casdoor vs Zitadel.

4. authentik

authentik is popular with self-hosters: visual login flows, OIDC, SAML, LDAP and RADIUS, and proxy outposts that put a login in front of apps without one.

Trade-offs: there's no hosted version, and enterprise features cost $5 per internal user or $0.02 per external user per month. See Casdoor vs authentik.

5. Logto

Logto is a TypeScript identity provider with a modern sign-in experience and organizations for B2B apps, self-hosted or on Logto Cloud (free tier with 50,000 MAU, Pro from $24 per month plus add-ons).

Trade-offs: in Logto Cloud, enterprise SSO, MFA and organizations are paid add-ons. See Casdoor vs Logto.

Which one should you choose?

• You want FusionAuth's model (one server, full console, hosted or self-hosted) with every feature free and a flat-priced cloud: Casdoor.
• You want the most widely deployed option and may buy support from Red Hat: Keycloak.
• You're building multi-tenant B2B SaaS and AGPL-3.0 is fine: Zitadel.
• You self-host apps that have no login of their own: authentik.
• You prefer a TypeScript codebase and a per-MAU cloud: Logto.

Migrating from FusionAuth to Casdoor

1. Export users with FusionAuth's API and import them into Casdoor. Casdoor can verify bcrypt, Argon2id, PBKDF2 and salted SHA-256 / SHA-512 hashes, so most users keep their passwords.
2. Recreate applications in Casdoor. Apps that use OpenID Connect or SAML only need a new issuer URL and client credentials.
3. Recreate social and enterprise identity providers, then move apps over one at a time.

Talk to us if you'd like help planning a migration.