Compare software

Isabelle vs Dafny: catalog facts
Isabelle	Dafny
Best for: Researchers and students working on formal mathematical proofs and verification	Best for: Developers who need formally verified code for critical logic
Free Free to download for Linux, Windows and macOS.	Free Free and open source under the MIT licence.
Windows, macOS, Linux	Windows, Command line
Long-established proof assistant with regular releases Bundled jEdit-based IDE with dark mode and screen reader support All 3 strengths for Isabelle Long-established proof assistant with regular releases Bundled jEdit-based IDE with dark mode and screen reader support Builds for Linux on Intel and ARM, Windows and macOS	Automated verification of code against specifications Compiles to C#, Java, JavaScript and Go All 4 strengths for Dafny Automated verification of code against specifications Compiles to C#, Java, JavaScript and Go Language server, formatter and IDE plugins included Extensive tutorials and reference manual
Large projects need a lot of memory, up to 64 GB Steep learning curve for those new to formal proof	Writing specifications takes extra effort and a learning curve Python compilation still in progress
Downloadable app	Downloadable app
Not open source	Open source
License not stated	License: MIT
No account needed	No account needed
Offline features available	Offline features available
Official website Full listing and sources Sources for Isabelle cl.cam.ac.uk/research/hvg/Isabelle Catalog checked October 2, 2026	Official website Full listing and sources Sources for Dafny dafny-lang.github.io/dafny Catalog checked October 2, 2026

“Not stated” means we have not confirmed it. Features can vary by device and plan.