HOL4 vs Lean
| HOL4 | Lean | |
|---|---|---|
| Free plan | Yes | Yes |
| Free trial | No | No |
| Paid from | Free | Free |
| Open source | No | No |
| Platforms | Linux, macOS, self-hosted, Windows | Linux, macOS, Web, Windows |
| Free plan | Yes | — |
| Supported formalisms | theorem-proving | theorem-proving |
| Counterexamples | Yes | — |
| Proof artifacts | Yes | Yes |
| Input languages | HOL higher-order logic; Standard ML | Lean 4 |
| Deployment | self-hosted | both |
| Verification method | — | deductive |
Both are listed in Best Formal Verification Tools. On Specifiction, Lean scores higher on our published basis.