Isabelle vs Viper
| Isabelle | Viper | |
|---|---|---|
| Free plan | Yes | No |
| Free trial | No | No |
| Paid from | Free | — |
| Open source | No | No |
| Platforms | Linux, macOS, self-hosted, Windows | extension, Linux, macOS, Web, Windows |
| Free plan | Yes | Yes |
| Verification method | deductive | hybrid |
| Supported formalisms | theorem-proving | contracts |
| Counterexamples | Yes | Yes |
| Proof artifacts | Yes | — |
| Input languages | Isabelle/Isar, Isabelle/Pure, ML; executable specifications can generate SML, OCaml, Haskell, and Scala | Viper language; Go, Python, and Rust via front-end tools |
| Deployment | self-hosted | self-hosted |
Both are listed in Best Formal Verification Tools. On The Geeks Club, Isabelle scores higher on our published basis.