Lean vs Stainless
| Lean | Stainless | |
|---|---|---|
| Free plan | No | No |
| Free trial | No | No |
| Paid from | — | — |
| Open source | No | No |
| Platforms | Linux, macOS, Web, Windows | Linux, macOS, Windows |
| Verification method | deductive | deductive |
| Supported formalisms | theorem-proving | contracts |
| Proof artifacts | Yes | — |
| Input languages | Lean 4 | Scala 3 |
| Deployment | both | self-hosted |
| Free plan | — | Yes |
| Counterexamples | — | Yes |
Both are listed in Best Formal Verification Tools. On Freedom251, Stainless scores higher on our published basis.