Alloy Analyzer vs Isabelle

Alloy Analyzer is a free model-checking tool for describing systems in the Alloy language and exploring the structures those descriptions permit. It searches for structures that satisfy constraints and for counterexamples to properties. Models can represent collections of structures that change over time, including security configurations and switching network topologies. The Analyzer presents results graphically, with appearance options that can be tailored to a domain. Alloy 6 adds mutable state, temporal logic, and temporal model checking; that checking requires NuSMV or nuXmv to be installed and available in PATH. The self-contained executable includes the Pardinus/Kodkod model finder, SAT solvers, the standard Alloy library, tutorial examples, and source code. The same JAR can be used as an API in other applications. Sterling adds a web-based visualizer with graph and table views, customizable and extendable with JavaScript. Alloy is self-hosted, supports Linux, macOS, Windows, and API use, and is maintained by volunteers.

Isabelle is a free proof assistant for expressing mathematical formulas in a formal language and proving them within a logical calculus. Its main applications are formalizing mathematics and verifying properties of hardware, software, programming languages, and protocols. Isabelle/HOL provides a higher-order logic environment for large applications, with tools for reasoning, simplification, linear arithmetic, algebraic decision procedures, and access to external first-order provers through Sledgehammer. Proofs can be written in Isar, a structured language intended to be understandable to people and computers. Isabelle/HOL can generate SML, OCaml, Haskell, and Scala code from executable specifications. Isabelle/jEdit is the default interface, providing ongoing proof checking and real-time feedback; the Isabelle2025-2 release also includes Isabelle/VSCode with panels for documentation, symbols, and Sledgehammer. The distribution includes a library of verified mathematics, supplemented by the Archive of Formal Proofs. Isabelle runs on Linux, macOS, Windows, and self-hosted deployments. Its main code base is subject to BSD-style regulations. Windows lacks developer signatures and certificates and is rejected by Microsoft by default at first launch; macOS requires users to allow the unsigned application to open.