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Rhai - Embedded Scripting for Rust

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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.
  • 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.

Protection 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.

To build The Book, first install mdbook and mdbook-tera (for templating). Running mdbook build builds it.


An Online Playground is available with syntax-highlighting editor. 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.


~50K SLoC