# WASM vs Native SDK

RivetKit ships two runtimes for executing actor logic. Most projects use the
native runtime automatically. Edge and serverless platforms that cannot run
native binaries use the WebAssembly runtime.

- **Native**: Default. Runs on Node.js and Bun via native bindings. Best performance.
- **WebAssembly (wasm)**: Runs anywhere a `WebAssembly.Module` can be instantiated, including Cloudflare Workers, Supabase Edge Functions, and Deno Deploy.

## Native runtime

The native runtime is the default and requires no configuration. It loads
platform-specific native bindings for the best performance and full feature
support on Node.js and Bun.

examples/docs/general-wasm-vs-native-sdk/native-runtime.ts:

```ts
import { actor, setup } from "rivetkit";

const counter = actor({ state: { count: 0 }, actions: {} });

const registry = setup({ use: { counter } });
```

## WebAssembly runtime

Edge platforms run on isolates (V8, Deno) that cannot load native binaries, so
RivetKit provides a WebAssembly build of its core runtime in the
`@rivetkit/rivetkit-wasm` package. You select it with `runtime: "wasm"` and pass
the wasm bindings and binary through the `wasm` option.

### Recommended: use a platform package

For supported platforms, use the dedicated package instead of wiring the wasm
runtime by hand. They install the wasm runtime, load the binary, and (on
Cloudflare) provide the outbound WebSocket the control plane tunnel needs.

- **Cloudflare Workers**: [`@rivetkit/cloudflare-workers`](/actors/docs/quickstart/cloudflare)
- **Supabase Edge Functions**: [`@rivetkit/supabase`](/actors/docs/quickstart/supabase)

```typescript @nocheck
// Cloudflare Workers
import { actor } from "rivetkit";
import { createHandler } from "@rivetkit/cloudflare-workers";

const counter = actor({ state: { count: 0 }, actions: {} });

export default createHandler({ use: { counter } });
```

### Manual configuration

For platforms without a dedicated package, configure the wasm runtime directly.
Pass the bindings from `@rivetkit/rivetkit-wasm` and the wasm binary as
`initInput`. `initInput` accepts a `Uint8Array`, `URL`, `Response`, or a
`WebAssembly.Module`.

```typescript @nocheck
import { actor, setup } from "rivetkit";
import * as wasmBindings from "@rivetkit/rivetkit-wasm";
import wasmModule from "@rivetkit/rivetkit-wasm/rivetkit_wasm_bg.wasm";

const counter = actor({ state: { count: 0 }, actions: {} });

const registry = setup({
  runtime: "wasm",
  wasm: { bindings: wasmBindings, initInput: wasmModule },
  use: { counter },
});
```

On platforms without an outbound `new WebSocket(url)` constructor (such as
Cloudflare Workers), you must also install a fetch-based `globalThis.WebSocket`
shim so the actor can open its tunnel to the control plane. The platform packages handle
this for you, which is why they are recommended.

## Related

- [Runtime Modes](/actors/docs/general/runtime-modes)
- [Cloudflare Workers Quickstart](/actors/docs/quickstart/cloudflare)
- [Supabase Functions Quickstart](/actors/docs/quickstart/supabase)