What is Isabelle?
Isabelle is a generic proof assistant. It allows mathematical formulas to be expressed in a formal language and provides tools for proving those formulas in a logical calculus. Isabelle was originally developed at the University of Cambridge and Technische Universität München, but now includes numerous contributions from institutions and individuals worldwide. See the Isabelle overview for a brief introduction.
Now available: Isabelle2025 (March 2025)
Download for Linux (Intel)
Download for Windows
Download for macOSHardware requirements:
- Small experiments: 4 GB memory, 2 CPU cores
- Medium applications: 8 GB memory, 4 CPU cores
- Large projects: 16 GB memory, 8 CPU cores
- Extra-large projects: 64 GB memory, 16 CPU cores
Some notable changes:
- Inner syntax: markup for blocks and type information about constants.
- Inner syntax: more scalable pretty-printing, based on bytes (blobs).
- Inner syntax: more efficient folding of term abbreviations.
- Inner syntax: more robust no_syntax declarations via bundles.
- HOL: various improvements of theory libraries.
- HOL: updates and improvements of Sledgehammer and external provers.
- HOL: various improvements to code generation.
- Isabelle/jEdit: various improvements to Output, including Search.
- Isabelle/VSCode: various improvements, concerning markup, completions etc.
- Document preparation: more markup for term output.
- ML: value-oriented pretty printing using explicit
Pretty.output_ops. - System: Find_Facts full-text search engine, with web interface.
- System: Build_Manager in Isabelle/Scala, as replacement for Jenkins.
- System: more scalable type
isabelle.Bytes, allow messages of many GiB.
See also the cumulative NEWS.
Distribution & Support
Isabelle is distributed for free under a conglomerate of open-source licenses, but the main code-base is subject to BSD-style regulations. The application bundles include source and binary packages and documentation, see the detailed installation instructions. A vast collection of Isabelle examples and applications is available from the Archive of Formal Proofs.
Support is available by the official documentation and mailing lists:
- The isabelle-users mailing list provides a forum for Isabelle users to discuss problems, exchange information, and make announcements. Users of official Isabelle releases should subscribe or see the archive.
- The isabelle-dev mailing list covers the Isabelle development process, including intermediate repository versions, and administrative issues concerning the website or testing infrastructure. Early adopters of development snapshots or repository versions should subscribe or see the archive.
Zulip Chat is a real-time discussion platform to exchange ideas, ask questions, and collaborate on Isabelle projects, with minimalistic public archive.
Stack Overflow and Stack Exchange are a question-and-answer platform, with complex review process but limited discussion facilities.