Isabelle

Isabelle provides a formal language for expressing mathematical formulas and a suite of tools for constructing proofs within a logical calculus. It supports interactive development of proofs, allowing users to write and check theories, invoke automated provers, and explore proof states through an integrated editor. The system is distributed for macOS, Linux, and Windows and includes the Archive of Formal Proofs, a large collection of verified examples and libraries.

The environment is built around the Prover IDE (PIDE) and offers a configurable jEdit front‑end with dark‑mode support, scalable SVG icons, and enhanced mouse handling, as well as a VSCode interface with panels for documentation, symbols, and the Sledgehammer automation tool. Command‑line options allow fine‑grained control of the underlying ML system and session management.

Isabelle is maintained by a community of academic institutions and contributors, released under open‑source licenses with BSD‑style terms for the main code. It is targeted at researchers, educators, and engineers who need a stable, extensible platform for formal verification and proof development.