How to use the Required Memo token extension
The MemoTransfer
extension enforces that every incoming transfer to a Token
Account is accompanied by a memo instruction.
This memo instruction records a message in the transaction's program logs. This
feature is particularly useful for adding context to transactions, making it
easier to understand their purpose when reviewing the transaction logs later.
In this guide, we'll walk through an example of 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
,
@solana/spl-token
, and @solana/spl-memo
libraries.
Replace the starter code with the following:
import {
Connection,
Keypair,
SystemProgram,
Transaction,
clusterApiUrl,
sendAndConfirmTransaction,
TransactionInstruction,
PublicKey,
} from "@solana/web3.js";
import {
ExtensionType,
TOKEN_2022_PROGRAM_ID,
createEnableRequiredMemoTransfersInstruction,
createInitializeAccountInstruction,
createMint,
disableRequiredMemoTransfers,
enableRequiredMemoTransfers,
getAccountLen,
createAccount,
mintTo,
createTransferInstruction,
} from "@solana/spl-token";
import { createMemoInstruction } from "@solana/spl-memo";
// Playground wallet
const payer = pg.wallet.keypair;
// Connection to devnet cluster
const connection = new Connection(clusterApiUrl("devnet"), "confirmed");
// Transaction to send
let transaction: Transaction;
// Transaction signature returned from sent transaction
let transactionSignature: string;
Mint Setup
We'll first need to create a new Mint Account before we can create Token Accounts.
// Authority that can mint new tokens
const mintAuthority = pg.wallet.publicKey;
// Decimals for Mint Account
const decimals = 2;
// Create Mint Account
const mint = await createMint(
connection,
payer, // Payer of the transaction and initialization fees
mintAuthority, // Mint Authority
null, // Optional Freeze Authority
decimals, // Decimals of Mint
undefined, // Optional keypair
undefined, // Options for confirming the transaction
TOKEN_2022_PROGRAM_ID, // Token Extension Program ID
);
Memo Transfer Token Account
Next, let's build a transaction to enable the MemoTransfer
extension for a new
Token Account.
First, let's generate a new keypair to use as the address of the Token Account.
// Random keypair to use as owner of Token Account
const tokenAccountKeypair = Keypair.generate();
// Address for Token Account
const tokenAccount = tokenAccountKeypair.publicKey;
Next, let's determine the size of the new Token Account and calculate the minimum lamports needed for rent exemption.
// Size of Token Account with extension
const accountLen = getAccountLen([ExtensionType.MemoTransfer]);
// Minimum lamports required for Token Account
const lamports = await connection.getMinimumBalanceForRentExemption(accountLen);
With Token Extensions, the size of the Token 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 Token Account data
- Enable the
MemoTransfer
extension
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: tokenAccount, // Address of the account to create
space: accountLen, // 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 Token Account data.
// Instruction to initialize Token Account data
const initializeAccountInstruction = createInitializeAccountInstruction(
tokenAccount, // Token Account Address
mint, // Mint Account
payer.publicKey, // Token Account Owner
TOKEN_2022_PROGRAM_ID, // Token Extension Program ID
);
Lastly, build the instruction to enable the MemoTransfer
extension for the
Token Account.
// Instruction to initialize the MemoTransfer Extension
const enableRequiredMemoTransfersInstruction =
createEnableRequiredMemoTransfersInstruction(
tokenAccount, // Token Account address
payer.publicKey, // Token Account Owner
undefined, // Additional signers
TOKEN_2022_PROGRAM_ID, // Token Program ID
);
Send Transaction
Next, let's add the instructions to a new transaction and send it to the
network. This will create a Token Account with the MemoTransfer
extension
enabled.
// Add instructions to new transaction
transaction = new Transaction().add(
createAccountInstruction,
initializeAccountInstruction,
enableRequiredMemoTransfersInstruction,
);
// Send transaction
transactionSignature = await sendAndConfirmTransaction(
connection,
transaction,
[payer, tokenAccountKeypair], // Signers
);
console.log(
"\nCreate Token Account:",
`https://solana.fm/tx/${transactionSignature}?cluster=devnet-solana`,
);
Run the script by clicking the Run
button. You can then inspect the
transaction details on SolanaFM.
Create and Fund Token Account
Next, let's set up another Token Account to demonstrate the functionality of the
MemoTransfer
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, mint 2 tokens to the sourceTokenAccount
to fund it.
// Mint tokens to sourceTokenAccount
transactionSignature = await mintTo(
connection,
payer, // Transaction fee payer
mint, // Mint Account address
sourceTokenAccount, // Mint to
mintAuthority, // Mint Authority address
200, // 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`,
);
Transfer and Memo Instruction
Next, let's prepare the token transfer and memo instructions.
First, build the instruction to transfer tokens from the sourceTokenAccount
to
the tokenAccount
which has the MemoTransfer
extension enabled.
// Instruction to transfer tokens
const transferInstruction = createTransferInstruction(
sourceTokenAccount, // Source Token Account
tokenAccount, // Destination Token Account
payer.publicKey, // Source Token Account owner
100, // Amount
undefined, // Additional signers
TOKEN_2022_PROGRAM_ID, // Token Extension Program ID
);
Next, build the memo instruction. The message will be included in the program logs of the transaction the instruction is added to.
// Message for the memo
const message = "Hello, Solana";
// Instruction to add memo
const memoInstruction = new TransactionInstruction({
keys: [{ pubkey: payer.publicKey, isSigner: true, isWritable: true }],
data: Buffer.from(message, "utf-8"),
programId: new PublicKey("MemoSq4gqABAXKb96qnH8TysNcWxMyWCqXgDLGmfcHr"),
});
Alternatively, you can create the instruction using the @solana/spl-memo
library:
// Message for the memo
const message = "Hello, Solana";
// Instruction to add memo
const memoInstruction = createMemoInstruction(message, [payer.publicKey]);
Attempt Transfer without Memo
To demonstrate the functionality of the MemoTransfer
extension, let's first
attempt to send a token transfer without a memo.
try {
// Attempt to transfer without memo
transaction = new Transaction().add(transferInstruction);
// Send transaction
await sendAndConfirmTransaction(
connection,
transaction,
[payer], // Signers
);
} 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: 0x24]
logs:
[ 'Program TokenzQdBNbLqP5VEhdkAS6EPFLC1PHnBqCXEpPxuEb invoke [1]',
'Program log: Instruction: Transfer',
'Program log: Error: No memo in previous instruction; required for recipient to receive a transfer',
'Program TokenzQdBNbLqP5VEhdkAS6EPFLC1PHnBqCXEpPxuEb consumed 6571 of 200000 compute units',
'Program TokenzQdBNbLqP5VEhdkAS6EPFLC1PHnBqCXEpPxuEb failed: custom program error: 0x24' ] }
Transfer with Memo
Next, send a token transfer with the memo instruction included on the transaction.
// Add instructions to new transaction
transaction = new Transaction().add(memoInstruction, transferInstruction);
// Send transaction
transactionSignature = await sendAndConfirmTransaction(
connection,
transaction,
[payer], // Signers
);
console.log(
"\nTransfer with Memo:",
`https://solana.fm/tx/${transactionSignature}?cluster=devnet-solana`,
);
Run the script by clicking the Run
button. You can then inspect the
transaction details on SolanaFM.
Enable and Disable Memo Transfer
The MemoTransfer
extension can also be freely enabled or disabled by the Token
Account owner.
To enable the MemoTransfer
extension, use the enableRequiredMemoTransfers
instruction.
// Enable Required Memo Transfers
transactionSignature = await enableRequiredMemoTransfers(
connection, // Connection to use
payer, // Payer of the transaction fee
tokenAccount, // Token Account to modify
payer.publicKey, // Owner of Token Account
undefined, // Additional signers
undefined, // Confirmation options
TOKEN_2022_PROGRAM_ID, // Token Extension Program ID
);
console.log(
"\nEnable Required Memo Transfers:",
`https://solana.fm/tx/${transactionSignature}?cluster=devnet-solana`,
);
To disable the MemoTransfer
extension, use the disableRequiredMemoTransfers
instruction.
// Disable Required Memo Transfers
transactionSignature = await disableRequiredMemoTransfers(
connection, // Connection to use
payer, // Payer of the transaction fee
tokenAccount, // Token Account to modify
payer.publicKey, // Owner of Token Account
undefined, // Additional signers
undefined, // Confirmation options
TOKEN_2022_PROGRAM_ID, // Token Extension Program ID
);
console.log(
"\nDisable Required Memo Transfers:",
`https://solana.fm/tx/${transactionSignature}?cluster=devnet-solana`,
);
Once the MemoTransfer
extension is disabled, transactions to transfer tokens
without a memo instruction will complete successfully.
// Add instructions to new transaction
transaction = new Transaction().add(transferInstruction);
// Send transaction
transactionSignature = await sendAndConfirmTransaction(
connection,
transaction,
[payer], // Signers
);
console.log(
"\nTransfer without Memo:",
`https://solana.fm/tx/${transactionSignature}?cluster=devnet-solana`,
);
Run the script by clicking the Run
button. You can then inspect the
transaction details on SolanaFM.
Conclusion
The MemoTransfer
extension ensures every incoming transfer to a Token Account
includes a memo. By requiring a memo instruction with each transfer, a message
is recorded in the transaction's program logs. This feature is especially useful
for understanding the purpose of transactions when reviewing logs at a later
time.