Comparison
How zwasm compares to other WebAssembly runtimes.
Overview
| Feature | zwasm | wasmtime | wasm3 | wasmer |
|---|---|---|---|---|
| Language | Zig | Rust | C | Rust/C |
| Binary size | 1.20 MB Mac / 1.56 MB Linux | ~56 MB | ~100–500 KB | 30+ MB |
| Memory (fib) | ~3.5 MB | ~12 MB | ~1 MB | ~15 MB |
| Execution | Interp + ARM64/x86_64 JIT | Cranelift AOT/JIT | Pure interpreter | LLVM/Cranelift/Singlepass |
| Wasm 3.0 | Full (all 9 proposals) | Full | Partial | Partial |
| GC proposal | Yes | Yes | No | No |
| SIMD | Full (256 ops, JIT) | Full | Partial | Full |
| WASI | P1 (46/46) + P2 (adapter) | P1 + P2 (native) | P1 (partial) | P1 + P2 |
| Platforms | macOS, Linux, Windows | macOS, Linux, Windows | Many (no JIT) | macOS, Linux, Windows |
When to choose zwasm
Small footprint: When binary size and memory usage matter. zwasm is roughly 35–47× smaller than wasmtime depending on platform, while still shipping the full Wasm 3.0 feature set.
Zig ecosystem: When embedding in a Zig application. zwasm integrates as a native zig build dependency with zero C dependencies.
Spec completeness: When you need full Wasm 3.0 support including GC, SIMD, threads, and exception handling in a small runtime.
Fast startup: The interpreter starts executing immediately. JIT compilation happens in the background for hot functions.
When to choose alternatives
Maximum throughput: wasmtime’s Cranelift AOT compiler produces highly optimized native code. For long-running compute-heavy workloads, wasmtime may be faster. SIMD microbenchmarks are competitive (matrix_mul beats wasmtime), but compiler-generated SIMD code shows larger gaps due to split v128 storage overhead.
Minimal size: wasm3 is ~100 KB and runs on microcontrollers. If you need the absolute smallest runtime without JIT, wasm3 may be a better fit.
WASI Preview 2: wasmtime has the most complete WASI P2 implementation. zwasm’s P2 support is via a P1 adapter layer.