Isabelle

Input—per 1M tokens

Output—per 1M tokens

Context—tokens

WeightsClosed

About

Isabelle is ranked #5 of 33 in formal verification tools on Inferse. It runs on Linux, macOS, Self-hosted, Windows. There is a free plan.

Compared on formal verification tools

Free plan: Yesisabelle.in.tum.de
Verification method: deductiveisabelle.in.tum.de
Supported formalisms: theorem-provingisabelle.in.tum.de
Counterexamples: Yesisabelle.in.tum.de
Proof artifacts: Yesisabelle.in.tum.de
Input languages: Isabelle/Isar, Isabelle/Pure, ML; executable specifications can generate SML, OCaml, Haskell, and Scalaisabelle.in.tum.de
Deployment: self-hostedisabelle.in.tum.de

Facts

What it does: Isabelle is a generic proof assistant for expressing mathematical formulas in a formal language and proving them in a logical calculus.isabelle.in.tum.de · 30 Sept 2026
Main uses: Its main applications are formalizing mathematical proofs and formal verification, including proving properties of hardware, software, programming languages, and protocols.isabelle.in.tum.de · 30 Sept 2026
Isabelle/HOL: Isabelle/HOL provides a higher-order logic theorem proving environment intended for large applications.isabelle.in.tum.de · 30 Sept 2026
Proof tools: Proof productivity tools include a classical reasoner, a simplifier, linear arithmetic automation, algebraic decision procedures, and access to external first-order provers through Sledgehammer.isabelle.in.tum.de · 30 Sept 2026
Proof language: Isar is a structured proof language whose proof text is intended to be understandable to both people and computers.isabelle.in.tum.de · 30 Sept 2026
Code generation: Isabelle/HOL can turn executable specifications into code in SML, OCaml, Haskell, and Scala.isabelle.in.tum.de · 30 Sept 2026
IDE: Isabelle/jEdit is the default user interface and Prover IDE, providing continuous proof checking with real-time feedback and semantic markup.isabelle.in.tum.de · 30 Sept 2026
Additional editor: The Isabelle2025-2 release includes Isabelle/VSCode, with GUI panels for Documentation, Symbols, and Sledgehammer.isabelle.in.tum.de · 30 Sept 2026
Platforms: The application bundles support Linux, Windows, and macOS; the site also provides a self-contained Docker image without GUI support.isabelle.in.tum.de · 30 Sept 2026
Libraries and examples: The distribution includes a large theory library of formally verified mathematics, and the Archive of Formal Proofs provides additional applications from mathematics and software engineering.isabelle.in.tum.de · 30 Sept 2026
Security design: The overview says Isabelle follows the LCF system approach so users can write proof procedures and theory extension packages in ML without breaking system soundness.isabelle.in.tum.de · 30 Sept 2026
Windows limitation: The Windows application lacks developer signatures and certificates, so Microsoft rejects it by default when first run.isabelle.in.tum.de · 30 Sept 2026
macOS limitation: The macOS application lacks developer signatures and certificates, so Apple rejects it by default and requires the user to allow it to open.isabelle.in.tum.de · 30 Sept 2026
Support: Support is available through official documentation, the isabelle-users and isabelle-dev mailing lists, Zulip, and Q&A sites listed by the project.isabelle.in.tum.de · 30 Sept 2026