Comparison
How zwasm compares to other WebAssembly runtimes.
Overview
| Feature | zwasm | wasmtime | wasm3 | wasmer |
|---|---|---|---|---|
| Language | Zig | Rust | C | Rust/C |
| Binary size | ~1.4 MB | 56 MB | ~100 KB | 30+ MB |
| Memory (fib) | 3.5 MB | 12 MB | ~1 MB | 15+ MB |
| Execution | Interp + JIT | AOT/JIT | Interpreter | AOT/JIT |
| Wasm 3.0 | Full | Full | Partial | Partial |
| GC proposal | Yes | Yes | No | No |
| SIMD | Full (256 ops) | Full | Partial | Full |
| WASI | P1 (46 syscalls) | P1 + P2 | P1 (partial) | P1 + P2 |
| Platforms | macOS, Linux | macOS, Linux, Windows | Many (no JIT) | macOS, Linux, Windows |
When to choose zwasm
Small footprint: When binary size and memory usage matter. zwasm is ~40x smaller than wasmtime.
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. In particular, SIMD-heavy workloads are currently ~22x slower on zwasm (stack interpreter, no SIMD JIT yet).
Windows support: zwasm currently supports macOS and Linux. For Windows, use wasmtime or wasmer.
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.