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A high-performance multi-language bindings generator for Rust, up to 1,000x faster than UniFFI. Ship Rust libraries that feels native to Swift, Kotlin, and more

647 starsRust

BoltFFI a high performance Rust bindings generator

by alihilal94·Feb 22, 2026·2 points·1 comment
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AI Analysis

●●●BangerWizardryBig BrainZero to One

Zero-copy FFI approach cuts UniFFI overhead by 200–1000x; async maps to native patterns.

Strengths
  • •Rigorous benchmarks with reproducible code—1000x speedup on echo_i32, 205–589x on real workloads vs UniFFI
  • •Zero-copy design fundamentally different from UniFFI's serialization model; primitives pass as raw values, structs as pointers
  • •Async/await, coroutines, and Promises map automatically to target language idioms—solves a real friction point in cross-language async
Weaknesses
  • •Ecosystem risk: UniFFI is Rust Foundation–backed; adoption depends on builders valuing speed over institutional weight
  • •Early stage: Swift/Kotlin stable, WASM partial, Python/C#/Java/Ruby still TBD—completeness matters for migration
Target Audience

Rust library authors targeting mobile and WASM; iOS/Android developers shipping Rust

Similar To

UniFFI · wasm-bindgen

Post Description

Built this because we were tired of fighting the same Rust FFI issues over and over we wanted one rust exports model that can generate bindings for Swift Kotlin and WASM and also handle packaging without a bunch of manual glue. We are also adding more targets over time including Python C# Java and Ruby

The main thing we cared about was boundary overhead so BoltFFI uses a different approach than UniFFI and the bench numbers are much better in our case, also async exports map to native async patterns on the target side.

few numbers from the current benches vs UniFFI

echo_i32 BoltFFI <1 ns UniFFI 1,416 ns speedup >1000x

counter_increment 1k calls BoltFFI 2,700 ns UniFFI 1,580,000 ns speedup 589x

generate_locations 10k BoltFFI 62,542 ns UniFFI 12,817,000 ns speedup 205x

benchmarks and code are in the repo and we compare against UniFFI and wasm-bindgen there.

repo: https://github.com/boltffi/boltffi

docs: https://www.boltffi.dev/docs/overview

benchmarks: https://github.com/boltffi/boltffi/tree/main/benchmarks

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