> For the complete documentation index, see [llms.txt](https://docs.fast.xyz/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.fast.xyz/sdk-references/core-sdk-execution/fast-sdk.md).

# fast-sdk

Fast-native account queries, signing, and transactions with @fastxyz/sdk

`@fastxyz/sdk` is the TypeScript SDK for Fast-native operations. The [package README](https://github.com/fastxyz/fast-sdk/blob/main/packages/fast-sdk/README.md) is the API reference for your installed version. EVM ↔ Fast movements belong to [`@fastxyz/allset-sdk`](/sdk-references/core-sdk-execution/allset-sdk.md).

## Install and choose a network

```bash
npm install @fastxyz/sdk
```

```ts
import { FastProvider, Signer, TransactionBuilder } from '@fastxyz/sdk';
import { mainnet, testnet } from '@fastxyz/sdk/networks';

const network = testnet; // change to mainnet for real-value operations
const provider = new FastProvider(network);
```

`FastProvider` uses the proxy **REST** API. The built-in network constants include the URL and network ID; mainnet uses `https://api.fast.xyz/proxy-rest`, while testnet uses `https://testnet.api.fast.xyz/proxy-rest`. The [JSON-RPC API](/api-reference/json-rpc-api.md) is a separate low-level interface, not the transport used by this SDK.

## Build, sign, and submit

```ts
const signer = new Signer(privateKey); // keep this secret out of logs and source control
const sender = await signer.getPublicKey();
const account = await provider.getAccountInfo({ address: sender });

const envelope = await new TransactionBuilder({
  networkId: network.networkId!,
  signer,
  nonce: account.nextNonce,
})
  .addTokenTransfer({ tokenId, recipient, amount: 1000n, userData: null })
  .sign();

const result = await provider.submitTransaction(envelope);
```

The builder does **not** take a provider or automatically fetch a nonce. Fetch the current nonce and select the network explicitly. Multiple operations may be batched in one Fast transaction. Other builders and multisig support are documented in the [package README](https://github.com/fastxyz/fast-sdk/blob/main/packages/fast-sdk/README.md).

If submission times out or the response is lost, do not assume it failed. Reconcile the transaction identity, certificate, account nonce, and any pending multisig proposal before deciding whether to resubmit. A freshly rebuilt transaction can have a different timestamp or nonce and is not a safe substitute for the exact signed envelope.

The SDK also provides account/token queries, Ed25519 message signing, address conversion, and `MultiSigWorkflow`. It does not provide an EVM wallet or a generic bridge. See the [REST reference](/api-reference/rest-api.md) for proxy API documentation.


---

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