33 releases (18 breaking)

0.19.10 Jan 14, 2021
0.19.9 Dec 30, 2020
0.19.6 Nov 24, 2020
0.17.0 Jul 13, 2020
0.2.0 Mar 26, 2016

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Rhai - Embedded Scripting for Rust

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Rhai logo

Rhai is an embedded scripting language and evaluation engine for Rust that gives a safe and easy way to add scripting to any application.

Supported targets and builds

  • All common CPU targets for Windows, Linux and MacOS.
  • WebAssembly (WASM)
  • no-std
  • Minimum Rust version 1.45

Standard features

  • Easy-to-use language similar to JavaScript+Rust with dynamic typing.
  • Fairly low compile-time overhead.
  • Fairly efficient evaluation (1 million iterations in 0.3 sec on a single core, 2.3 GHz Linux VM).
  • Tight integration with native Rust functions and types, including getters/setters, methods and indexers.
  • Freely pass Rust variables/constants into a script via an external Scope - all clonable Rust types are supported; no need to implement any special trait.
  • Easily call a script-defined function from Rust.
  • Relatively little unsafe code (yes there are some for performance reasons).
  • Few dependencies (currently only smallvec).
  • Re-entrant scripting engine can be made Send + Sync (via the sync feature).
  • Scripts are optimized (useful for template-based machine-generated scripts) for repeated evaluations.
  • Easy custom API development via plugins system powered by procedural macros.
  • Function overloading and operator overloading.
  • Dynamic dispatch via function pointers with additional support for currying.
  • Closures (anonymous functions) that can capture shared values.
  • Some syntactic support for object-oriented programming (OOP).
  • Organize code base with dynamically-loadable modules.
  • Serialization/deserialization support via serde (requires the serde feature).
  • Support for minimal builds by excluding unneeded language features.

Protected against attacks

  • Sand-boxed - the scripting engine, if declared immutable, cannot mutate the containing environment unless explicitly permitted.
  • Rugged - protected against malicious attacks (such as stack-overflow, over-sized data, and runaway scripts etc.) that may come from untrusted third-party user-land scripts.
  • Track script evaluation progress and manually terminate a script run.

For those who actually want their own language


See The Rhai Book for details on the Rhai scripting engine and language.


An Online Playground is available with syntax-highlighting editor, powered by WebAssembly.

Scripts can be evaluated directly from the editor.


Licensed under either of the following, at your choice:

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


~53K SLoC