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Introduction

WeaveFFI generates type-safe bindings for 11 languages from a single IDL — no hand-written JNI, no duplicate implementations, no unsafe boilerplate.

Define your API once in YAML, JSON, or TOML; ship idiomatic packages for C, C++, Swift, Kotlin/Android, Node.js, WebAssembly, Python, .NET, Dart, Go, and Ruby that all talk to the same stable C ABI.

WeaveFFI works with any native library that exposes a stable C ABI — whether it’s written in Rust, C, C++, Zig, or another language. Rust gets first-class scaffolding via weaveffi generate --scaffold; other backends implement the symbols declared in the generated C header directly.

Why WeaveFFI?

  • One IDL, eleven languages. Describe your API once and ship packages to npm, SwiftPM, Maven, PyPI, NuGet, pub.dev, RubyGems, and Go modules.
  • Stable C ABI underneath. Every target speaks to the same extern "C" contract, so adding a new platform later is a code-gen change, not a rewrite.
  • Idiomatic per-target output. No lowest-common-denominator surface area. Swift gets async/await and throws, Kotlin gets suspend and JNI glue, Python gets typed .pyi stubs, TypeScript gets Promises, Dart gets dart:ffi — all from the same definition.

Design principle: standalone generated packages

Generated packages are fully self-contained and publishable to their native ecosystem (npm, CocoaPods, Maven Central, PyPI, NuGet, pub.dev, RubyGems, etc.) without requiring consumers to install WeaveFFI tooling or runtime dependencies. WeaveFFI is a build-time tool for library authors — consumers should never need to know it exists. Helper code (error types, memory management utilities) is generated inline into each package rather than pulled from a shared runtime dependency.

Where to next

  • Getting Started — install → IDL → generate → call from C.
  • Comparison — feature matrix vs UniFFI, cbindgen, diplomat, SWIG, autocxx, and an honest “when to choose WeaveFFI” guide.
  • FAQ — runtime cost, customization, Windows support, distribution, licensing.
  • Samples — the kitchen-sink kvstore reference plus calculator/contacts/inventory walkthroughs.
  • Generators — per-target reference for each of the eleven languages.
  • Guides — memory ownership, error handling, async, configuration.