Lean vs Why3
| Lean | Why3 | |
|---|---|---|
| Free plan | Yes | Yes |
| Free trial | No | No |
| Paid from | Free | Free |
| Open source | No | No |
| Platforms | Linux, macOS, Web, Windows | api, Linux, self-hosted, Web, Windows |
| Verification method | deductive | deductive |
| Supported formalisms | theorem-proving | contracts |
| Proof artifacts | Yes | — |
| Input languages | Lean 4 | WhyML, micro-C, micro-Python, MLCFG, Coma |
| Deployment | both | both |
| Counterexamples | — | Yes |
Both are listed in Best Formal Verification Tools. On Freedom251, Lean scores higher on our published basis.