Fly.io vs Keycloak
The ultimate side-by-side head-to-head analysis for 2026.
Short answer
- Price: not directly comparable — Fly.io is free tier available, Keycloak is free.
- How to start: Fly.io is free tier available, Keycloak is free.
These lines are generated from the pricing we track, not from a paid placement. We do not publish a quality score, because we do not have one we can stand behind. They cannot tell you which tool fits your workflow — the sections below are there for that. How we score tools.
Fly.io
Keycloak
Category
Developer Tools
Developer Tools
Base Price
Free tier
Free
Public API
Yes
Yes
Mobile app
No
No
Open source / self-hostable
No
Yes
SSO (SAML)
Yes
Yes
Choose Fly.io if:
Teams with users spread across continents who care about latency.
Choose Keycloak if:
Organisations that need enterprise identity without a per-user bill.
Fly.io: pros & cons
- Genuinely easy multi-region deployment
- Runs full containers, not a restricted runtime
- Good fit for latency-sensitive workloads
- Multi-region data is still your problem to solve
- Operational rough edges reported by users
- Pricing needs attention once you add regions
Keycloak: pros & cons
- Full identity server at no licence cost
- Standards support including SAML and OIDC
- Complete control over user data
- Operating it is a real responsibility
- Administration console is dense
- Upgrades need care
Our verdict on Fly.io
Compelling when latency actually matters. Single-region apps get little benefit from the added complexity.
Our verdict on Keycloak
The serious open-source answer to Auth0. Budget for the operations, because the licence saving is not free.