> ## Documentation Index
> Fetch the complete documentation index at: https://docs.turnkey.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Builder codes with Turnkey on Base

## Overview

[Builder Codes (ERC-8021)](https://www.erc8021.com/) allow app developers to attribute onchain activity to their application. This guide explains how to integrate Builder Code attribution on Base with Turnkey-signed transactions using viem's `dataSuffix` option.

By appending an encoded Builder Code to transaction data, you can track usage analytics on [base.dev](https://base.dev) and qualify for potential future rewards.

## Getting started

The first step is to set up your Turnkey organization and account. By following the [Quickstart guide](/getting-started/quickstart), you should have:

* A root user with a public/private API key pair within the Turnkey parent organization
* An organization ID

You'll also need:

* A wallet with an Ethereum account created within this organization, funded with ETH on Base Mainnet
* A Builder Code from [base.dev](https://base.dev) (found under **Settings** > **Builder Code**)
* `viem` version `2.45.0` or higher

## Encode your builder code

Builder codes are displayed in their decoded format on base.dev (e.g. `bc_b7k3p9da`). They need to be encoded into a hex `dataSuffix` (ending in `80218021`) before use.

Use the `ox` package to encode your Builder Code:

<CodeGroup>
  ```bash npm theme={"system"}
  npm i ox
  ```

  ```bash pnpm theme={"system"}
  pnpm add ox
  ```

  ```bash yarn theme={"system"}
  yarn add ox
  ```
</CodeGroup>

```tsx theme={"system"}
import { Attribution } from "ox/erc8021";

// Get your Builder Code from base.dev > Settings > Builder Codes
const DATA_SUFFIX = Attribution.toDataSuffix({
  codes: ["YOUR-BUILDER-CODE"], // e.g. "bc_b7k3p9da"
});
```

## Set up the Turnkey signer with attribution

This example uses `@turnkey/sdk-server` with `@turnkey/viem` to create a Turnkey signer and configure the wallet client with the `dataSuffix` option. The same approach works with any of our client-side SDKs (React, React Native, Flutter, etc.) since the `dataSuffix` configuration is handled at the viem wallet client level.

<CodeGroup>
  ```bash npm theme={"system"}
  npm i @turnkey/viem @turnkey/sdk-server
  ```

  ```bash pnpm theme={"system"}
  pnpm add @turnkey/viem @turnkey/sdk-server
  ```

  ```bash yarn theme={"system"}
  yarn add @turnkey/viem @turnkey/sdk-server
  ```
</CodeGroup>

```tsx theme={"system"}
import { base } from "viem/chains";
import { createAccount } from "@turnkey/viem";
import { Turnkey as TurnkeyServerSDK } from "@turnkey/sdk-server";
import {
  createWalletClient,
  http,
  type Account,
  createPublicClient,
} from "viem";

const turnkeyClient = new TurnkeyServerSDK({
  apiBaseUrl: process.env.TURNKEY_BASE_URL!,
  apiPrivateKey: process.env.NONROOT_API_PRIVATE_KEY!,
  apiPublicKey: process.env.NONROOT_API_PUBLIC_KEY!,
  defaultOrganizationId: process.env.TURNKEY_ORGANIZATION_ID!,
});

const turnkeyAccount = await createAccount({
  client: turnkeyClient.apiClient(),
  organizationId: process.env.TURNKEY_ORGANIZATION_ID!,
  signWith: process.env.SIGN_WITH!,
});

const client = createWalletClient({
  account: turnkeyAccount as Account,
  chain: base,
  transport: http(
    `https://base-mainnet.infura.io/v3/${process.env.INFURA_API_KEY!}`,
  ),
  dataSuffix: DATA_SUFFIX, // Appends Builder Code to all transactions
});

// Use the standard viem client for non-signing operations
const publicClient = createPublicClient({
  transport: http(
    `https://base-mainnet.infura.io/v3/${process.env.INFURA_API_KEY!}`,
  ),
  chain: base,
});
```

## Send a transaction

With the `dataSuffix` configured at the client level, all transactions automatically include your Builder Code. No changes are needed to individual transaction calls.

```tsx theme={"system"}
import { parseEther } from "viem";

const hash = await client.sendTransaction({
  to: "0x70997970c51812dc3a010c7d01b50e0d17dc79c8",
  value: parseEther("0.01"),
});

console.log("Transaction:", `https://basescan.org/tx/${hash}`);
```

## Verify attribution

To confirm your Builder Code is being appended correctly:

1. **Check base.dev:** Visit [base.dev](https://base.dev), select **Onchain** from the transaction type dropdown, and verify your attribution counts are incrementing under Total Transactions.

2. **Use a block explorer:** Find your transaction on [Basescan](https://basescan.org), view the input data field, and verify the last 16 bytes contain the `8021` repeating pattern. Decode the suffix to confirm your Builder Code is present.

3. **Use the open source validation tool:** Use the [Builder Code Validation](https://builder-code-checker.vercel.app/) tool to check a transaction or UserOperation hash for attribution.

## Resources

* [Base Builder Codes documentation](https://docs.base.org/base-chain/builder-codes/builder-codes)
* [ERC-8021 specification](https://www.erc8021.com/)
* [Turnkey viem integration](/sdks/web3/viem)
* [Turnkey policy engine](/concepts/policies/overview)