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What is a “Builder Code” and where do I get one?

A Builder Code is an ASCII string (like "baseapp" or "bc_xyz456") that identifies your application in the ERC-8021 attribution system. When your app’s transactions include this code, protocols can identify and reward you.
Obtain your Builder Code here.

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What are the benefits of supporting Builder Codes?

  • Rewards: If your app drives transactions, Builder Codes let Base automatically attribute that usage back to you, unlocking rewards as our program expands.
  • Analytics: Developers can reliably track onchain usage, user acquisition, and conversion metrics in Base.dev.
  • Visibility: Apps with Builder Codes can show up in discovery surfaces like our App Leaderboards, Base App store, and ecosystem spotlights.

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Do I need to modify my smart contracts to use ERC-8021?

No. The attribution suffix is appended to the end of transaction calldata. Smart contracts execute normally and ignore the extra data. Attribution is extracted by offchain indexers after the fact. This means:
  • Any existing smart contract automatically supports ERC-8021
  • No upgrades or redeployments required
  • Zero impact on contract execution

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How much additional gas do Builder Codes cost?

The ERC-8021 suffix adds a negligible amount of gas to each transaction at 16 gas per non-zero byte.

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Will Builder Codes expose my identity?

No. Builder Codes only associate transactions with your application—they don’t expose any wallet information that isn’t already public onchain.

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Can I use ERC-8021 with Externally Owned Accounts (EOAs)?

Yes. ERC-8021 works with both EOAs and smart contract wallets.

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How do I verify that my transaction was properly attributed?

1. Check base.dev
  • Visit base.dev
  • Select Onchain from the transaction type dropdown
  • Under the Total Transactions section, attribution counts increment when transactions with your code are processed
2. Use a Block Explorer (Basescan, Etherscan, etc.)
  • Find your transaction hash
  • View the input data field
  • Verify the last 16 bytes are the 8021 repeating.
  • Decode the suffix to confirm your Builder Code is present
3. Open Source Tools
  • Use the Builder Code Validation tool
  • Select transaction type
  • Enter the transaction or UserOperation hash
  • Click the Check Attribution button

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What wallets and SDKs currently support ERC-8021?

EOAs: All EOA wallets support dataSuffix by default. SDKs:
  • viem/wagmi - TypeScript SDK with native dataSuffix parameter support for server-side and client-side transactions
This requires [email protected] or higher
Embedded Wallets:
  • Privy - Embedded wallet solution with ERC-8021 capability
  • Turnkey - Infrastructure for programmatic wallets
Smart Wallets: Wallets supporting ERC-5792 can use the DataSuffixCapability for clean suffix appending: 
await wallet.sendCalls({
  calls: [...],
  capabilities: {
    dataSuffix: {
      value: "0x07626173656170700080218021802180218021802180218021"
      optional: true
    }
  }
});

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Additional Resources