Dafny is a verification-aware programming language
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Dafny is a programming language with a program verifier. As you type in your program, the verifier constantly looks over your shoulders and flags any errors. Dafny is currently spread across 3 sites:


You can ask questions about Dafny on Stack Overflow or participate in general discussion on the mailing list.

Try Dafny

The easiest way to get started with Dafny is to use rise4fun, where you can write and verify Dafny programs without having install anything. On rise4fun, you will also find the online Dafny tutorial.


See installation instructions on the wiki and instructions for installing the Dafny mode for Emacs.

Read more

Here are some ways to get started with Dafny:

The language itself draws pieces of influence from:

  • Euclid (from the mindset of a designing a language whose programs are to be verified),
  • Eiffel (like the built-in contract features),
  • CLU (like its iterators, and inspiration for the out-parameter syntax),
  • Java, C#, and Scala (like the classes and traits, and syntax for functions),
  • ML (like the module system, and its functions and inductive datatypes), and
  • Coq and VeriFast (like the ability to include co-inductive datatypes and being able to write inductive and co-inductive proofs).

External contributions

Code of Conduct

This project has adopted the Microsoft Open Source Code of Conduct. For more information see the Code of Conduct FAQ or contact opencode@microsoft.com with any additional questions or comments.


Dafny itself is licensed under the MIT license. (See LICENSE.txt in the root directory for details.) The subdirectory third_party contains third party material; see NOTICES.txt for more details.