halo2 Crates.io


Minimum Supported Rust Version

Requires Rust 1.56.1 or higher.

Minimum supported Rust version can be changed in the future, but it will be done with a minor version bump.

Controlling parallelism

halo2 currently uses rayon for parallel computation. The RAYON_NUM_THREADS environment variable can be used to set the number of threads.


Licensed under either of

  • Apache License, Version 2.0, (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
  • MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)

at your option.


Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.