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# Platform Compatibility

Viem targets modern ESM runtimes. The package declares Node.js `>=24.5` and includes integration
tests for Bun, Next.js, Node.js, and Vite.

| Platform | Support | Notes |
| --- | --- | --- |
| Modern browsers | Supported | Current Chrome, Edge, Firefox, and Safari releases with the required Web APIs. |
| Node.js | `>=24.5` | Matches the package `engines` requirement. |
| Bun | Supported | Covered by the Viem runtime environment tests. |
| Next.js | Supported | Covered by the Viem framework integration tests. |
| Vite | Supported | Covered by the Viem browser integration tests. |
| Deno | npm/ESM compatibility | Install from npm with `deno add npm:viem@next`. See the compatibility caveat below. |

:::warning
Deno support is based on its npm and ESM compatibility and is not currently covered by Viem v3
continuous integration. Test your application against its target Deno release.
:::

Deno restricts network access by default. Grant only the RPC hosts your application needs with
[`--allow-net`](https://docs.deno.com/runtime/reference/permissions/).

## Runtime APIs

The APIs Viem needs depend on the modules and transports your application uses.

| API | Usage |
| --- | --- |
| `BigInt` | Ethereum quantities, balances, fees, and block numbers. |
| `TextEncoder` and `TextDecoder` | String, byte, and hexadecimal encoding. |
| `fetch`, `Headers`, and `Response` | HTTP JSON-RPC, offchain reads, and fetched metadata. |
| `AbortController` and `AbortSignal` | Request cancellation and timeouts. |
| `crypto.getRandomValues` | Random keys and bytes. |
| `WebAssembly` | The optional `viem/wasm` cryptography Engine. |

Modern browsers, Node.js `>=24.5`, Bun, and current Deno releases provide these APIs. A different
runtime must provide standards-compatible implementations for the features it uses.

## Feature Requirements

### TypeScript

Viem requires TypeScript `>=5.9` when type checking against its APIs. Earlier compilers exceed
instantiation limits on Viem's inference-heavy types.

### WebSocket Transport

The [`webSocket`](/docs/transports/websocket) transport requires a global `WebSocket`
implementation. Modern browsers, Node.js `>=24.5`, Bun, and Deno provide one.

### WebAuthn and Web Crypto

Browser passkey creation and signing require `navigator.credentials`, `PublicKeyCredential`, and a
[secure context](https://developer.mozilla.org/en-US/docs/Web/Security/Secure_Contexts).

Support varies by browser and authenticator. See the
[Web Authentication API](https://developer.mozilla.org/en-US/docs/Web/API/Web_Authentication_API)
compatibility data before choosing passkey features.

Features that use Web Crypto P256 or encryption also require `globalThis.crypto.subtle`.

### WASM & Engines

The [`viem/wasm` Engine](/docs/guides/engine#install-the-wasm-engine) requires WebAssembly. The
[`viem/node` Engine](/docs/guides/engine#install-the-node-engine) uses `node:crypto` and must not be imported
into browser bundles.

## Runtime Entrypoints

| Entrypoint | Purpose |
| --- | --- |
| `viem` | Portable Clients, Actions, transports, accounts, chains, types, and Engine configuration. |
| `viem/node` | Node.js cryptography Engine, IPC transport, and trusted setup helpers. Do not import it into browser bundles. |
| `viem/wasm` | Portable WebAssembly cryptography Engine. |
| `viem/window` | TypeScript augmentation for `window.ethereum`. It does not install a wallet provider at runtime. |

Import `viem/window` once when a browser TypeScript project needs the injected provider typed:

```ts
import 'viem/window'

window.ethereum?.request({ method: 'eth_chainId' })
```