Token Extensions: Non-transferable

The NonTransferable extension makes it possible to create tokens that cannot be transferred. This enables the creation of "soul-bound" tokens, where digital assets are intrinsically linked to an individual. While these tokens cannot be transferred, the owner can still burn tokens and close the Token Account. This prevents users from being "stuck" with an unwanted asset.

In this guide, we will walk through an example of creating "soul-bound" tokens with the NonTransferable extension using Solana Playground. Here is the final script.

Getting Started

Start by opening this Solana Playground link with the following starter code.

// Client
console.log("My address:", pg.wallet.publicKey.toString());
const balance = await pg.connection.getBalance(pg.wallet.publicKey);
console.log(`My balance: ${balance / web3.LAMPORTS_PER_SOL} SOL`);

If it is your first time using Solana Playground, you'll first need to create a Playground Wallet and fund the wallet with devnet SOL.

If you do not have a Playground wallet, you may see a type error within the editor on all declarations of pg.wallet.publicKey. This type error will clear after you create a Playground wallet.

To get devnet SOL, run the solana airdrop command in the Playground's terminal, or visit this devnet faucet.

solana airdrop 5

Once you've created and funded the Playground wallet, click the "Run" button to run the starter code.

Add Dependencies

Let's start by setting up our script. We'll be using the @solana/web3.js and @solana/spl-token libraries.

Replace the starter code with the following:

import {
  Connection,
  Keypair,
  SystemProgram,
  Transaction,
  clusterApiUrl,
  sendAndConfirmTransaction,
} from "@solana/web3.js";
import {
  ExtensionType,
  TOKEN_2022_PROGRAM_ID,
  createInitializeMintInstruction,
  createInitializeNonTransferableMintInstruction,
  getMintLen,
  mintTo,
  createAccount,
  transfer,
  burn,
  closeAccount,
} from "@solana/spl-token";

// Playground wallet
const payer = pg.wallet.keypair;

// Connection to devnet cluster
const connection = new Connection(clusterApiUrl("devnet"), "confirmed");

// Transaction signature returned from sent transaction
let transactionSignature: string;

Mint Setup

First, let's define the properties of the Mint Account we'll be creating in the following step.

// Generate new keypair for Mint Account
const mintKeypair = Keypair.generate();
// Address for Mint Account
const mint = mintKeypair.publicKey;
// Decimals for Mint Account
const decimals = 2;
// Authority that can mint new tokens
const mintAuthority = pg.wallet.publicKey;

Next, let's determine the size of the new Mint Account and calculate the minimum lamports needed for rent exemption.

// Size of Mint Account with extension
const mintLen = getMintLen([ExtensionType.NonTransferable]);
// Minimum lamports required for Mint Account
const lamports = await connection.getMinimumBalanceForRentExemption(mintLen);

With Token Extensions, the size of the Mint Account will vary based on the extensions enabled.

Build Instructions

Next, let's build the set of instructions to:

Create a new account
Initialize the NonTransferable extension
Initialize the remaining Mint Account data

First, build the instruction to invoke the System Program to create an account and assign ownership to the Token Extensions Program.

// Instruction to invoke System Program to create new account
const createAccountInstruction = SystemProgram.createAccount({
  fromPubkey: payer.publicKey, // Account that will transfer lamports to created account
  newAccountPubkey: mint, // Address of the account to create
  space: mintLen, // Amount of bytes to allocate to the created account
  lamports, // Amount of lamports transferred to created account
  programId: TOKEN_2022_PROGRAM_ID, // Program assigned as owner of created account
});

Next, build the instruction to initialize the NonTransferable extension for the Mint Account.

// Instruction to initialize the NonTransferable Extension
const initializeNonTransferableMintInstruction =
  createInitializeNonTransferableMintInstruction(
    mint, // Mint Account address
    TOKEN_2022_PROGRAM_ID, // Token Extension Program ID
  );

Lastly, build the instruction to initialize the rest of the Mint Account data. This is the same as with the original Token Program.

// Instruction to initialize Mint Account data
const initializeMintInstruction = createInitializeMintInstruction(
  mint, // Mint Account Address
  decimals, // Decimals of Mint
  mintAuthority, // Designated Mint Authority
  null, // Optional Freeze Authority
  TOKEN_2022_PROGRAM_ID, // Token Extension Program ID
);

Send Transaction

Next, let's add the instructions to a new transaction and send it to the network. This will create a Mint Account with the NonTransferable extension enabled.

// Add instructions to new transaction
const transaction = new Transaction().add(
  createAccountInstruction,
  initializeNonTransferableMintInstruction,
  initializeMintInstruction,
);

// Send transaction
transactionSignature = await sendAndConfirmTransaction(
  connection,
  transaction,
  [payer, mintKeypair], // Signers
);

console.log(
  "\nCreate Mint Account:",
  `https://solana.fm/tx/${transactionSignature}?cluster=devnet-solana`,
);

Run the script by clicking the Run button. You can then inspect the transaction on the SolanaFM.

Create Token Accounts

Next, let's set up two Token Accounts to demonstrate the functionality of the NonTransferable extension.

First, create a sourceTokenAccount owned by the Playground wallet.

// Create Token Account for Playground wallet
const sourceTokenAccount = await createAccount(
  connection,
  payer, // Payer to create Token Account
  mint, // Mint Account address
  payer.publicKey, // Token Account owner
  undefined, // Optional keypair, default to Associated Token Account
  undefined, // Confirmation options
  TOKEN_2022_PROGRAM_ID, // Token Extension Program ID
);

Next, generate a random keypair and use it as the owner of a destinationTokenAccount.

// Random keypair to use as owner of Token Account
const randomKeypair = new Keypair();
// Create Token Account for random keypair
const destinationTokenAccount = await createAccount(
  connection,
  payer, // Payer to create Token Account
  mint, // Mint Account address
  randomKeypair.publicKey, // Token Account owner
  undefined, // Optional keypair, default to Associated Token Account
  undefined, // Confirmation options
  TOKEN_2022_PROGRAM_ID, // Token Extension Program ID
);

Lastly, mint 1 token to the sourceTokenAccount to test the non-transferrable enforcement.

// Mint tokens to sourceTokenAccount
transactionSignature = await mintTo(
  connection,
  payer, // Transaction fee payer
  mint, // Mint Account address
  sourceTokenAccount, // Mint to
  mintAuthority, // Mint Authority address
  100, // Amount
  undefined, // Additional signers
  undefined, // Confirmation options
  TOKEN_2022_PROGRAM_ID, // Token Extension Program ID
);

console.log(
  "\nMint Tokens:",
  `https://solana.fm/tx/${transactionSignature}?cluster=devnet-solana`,
);

Attempt Token Transfer

Next, let's try to transfer tokens from the sourceTokenAccount to the destinationTokenAccount. We expect this transaction to fail due to the NonTransferable extension.

try {
  // Attempt to Transfer tokens
  await transfer(
    connection,
    payer, // Transaction fee payer
    sourceTokenAccount, // Transfer from
    destinationTokenAccount, // Transfer to
    payer.publicKey, // Source Token Account owner
    100, // Amount
    undefined, // Additional signers
    undefined, // Confirmation options
    TOKEN_2022_PROGRAM_ID, // Token Extension Program ID
  );
} catch (error) {
  console.log("\nExpect Error:", error);
}

Run the script by clicking the Run button. You can then inspect the error in the Playground terminal. You should see a message similar to the following:

Expect Error: { [Error: failed to send transaction: Transaction simulation failed: Error processing Instruction 0: custom program error: 0x25]
  logs:
   [ 'Program TokenzQdBNbLqP5VEhdkAS6EPFLC1PHnBqCXEpPxuEb invoke [1]',
     'Program log: Instruction: Transfer',
     'Program log: Transfer is disabled for this mint',
     'Program TokenzQdBNbLqP5VEhdkAS6EPFLC1PHnBqCXEpPxuEb consumed 3454 of 200000 compute units',
     'Program TokenzQdBNbLqP5VEhdkAS6EPFLC1PHnBqCXEpPxuEb failed: custom program error: 0x25' ] }

Burn Tokens and Close Token Account

While tokens can't be transferred, they can still be burned.

// Burn tokens
transactionSignature = await burn(
  connection,
  payer, // Transaction fee payer
  sourceTokenAccount, // Burn from
  mint, // Mint Account address
  payer.publicKey, // Token Account owner
  100, // Amount
  undefined, // Additional signers
  undefined, // Confirmation options
  TOKEN_2022_PROGRAM_ID, // Token Extension Program ID
);

console.log(
  "\nBurn Tokens:",
  `https://solana.fm/tx/${transactionSignature}?cluster=devnet-solana`,
);

The Token Account can then be closed to recover the SOL that was allocated to the account. Note that the token balance must be 0.

// Close Token Account
transactionSignature = await closeAccount(
  connection,
  payer, // Transaction fee payer
  sourceTokenAccount, // Token Account to close
  payer.publicKey, // Account to receive lamports from closed account
  payer.publicKey, // Owner of Token Account
  undefined, // Additional signers
  undefined, // Confirmation options
  TOKEN_2022_PROGRAM_ID, // Token Extension Program ID
);

console.log(
  "\nClose Token Account:",
  `https://solana.fm/tx/${transactionSignature}?cluster=devnet-solana`,
);