Standard WebAssembly

V8 compiles and runs WebAssembly. The standard JavaScript API works as usual:

const bytes = require("node:fs").readFileSync("add.wasm");
const { instance } = await WebAssembly.instantiate(bytes, {});
instance.exports.add(1, 2);

WebAssembly.compileStreaming and WebAssembly.instantiateStreaming are Stable. They accept a Response or a Promise<Response> and consume the body without routing it through a string.

const { instance } = await WebAssembly.instantiateStreaming(fetch("https://example.com/add.wasm"));

amber:wasm (Preview)

amber:wasm adds host helpers so JavaScript and WebAssembly can share a backing store instead of copying buffers:

WebAssembly.Memory.buffer can share pages with a V8 ArrayBuffer.
Large .wasm files are memory-mapped on load instead of copied into the isolate first.

const wasm = require("amber:wasm");

const memory = new WebAssembly.Memory({ initial: 1 });
const shared = wasm.shareMemory(memory);

shared.uint8[0] = 77;      // writes straight into linear memory
shared.float32[1] = 3.14;  // bytes 4..8
shared.ptr;                // bigint host address of linear memory

memory.asUint8Array(0, 1)[0]; // 77

This module is Preview. Its API may change, and it is covered by tests/wasm_zero_copy_tests.rs rather than a Stable contract. The FFI pointer helpers and Tensor views on the same module are Preview too.

Not claimed

A custom Wasm compiler or JIT. V8 does the work.
WASI. There is no drop-in WASI host.