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Idris vs Isabelle: catalog facts
Idris	Isabelle
Free Free and open source under the BSD 3-Clause licence.	Free Free to download for Linux, Windows and macOS.
Windows, Command line	Windows, macOS, Linux
Types are first-class and can describe precise program properties Compiler can check assumptions and proofs before the program runs	Long-established proof assistant with regular releases Bundled jEdit-based IDE with dark mode and screen reader support
Small ecosystem compared with mainstream languages Dependent types have a steep learning curve	Large projects need a lot of memory, up to 64 GB Steep learning curve for those new to formal proof
Downloadable app	Downloadable app
Open source	Closed source
License: BSD-3-Clause	License not stated
No account needed	No account needed
Works offline	Works offline
Official website Full listing and sources Checked October 2, 2026	Official website Full listing and sources Checked October 2, 2026

Catalog facts only. Anything “not stated” is unconfirmed. Check full listings for details.