Skip to content
Algorand Developer Portal

Transaction Parameters

← Back to Algod Client

Description

Section titled “Description”

This example demonstrates how to get suggested transaction parameters using suggestedParams() and transactionParams() methods. These parameters are essential for constructing valid transactions on the Algorand network.

Prerequisites

Section titled “Prerequisites”
  • LocalNet running (via algokit localnet start)

Run This Example

Section titled “Run This Example”

From the repository root:

Terminal window
cd examples
npm run example algod_client/05-transaction-params.ts

Code

Section titled “Code”

View source on GitHub

05-transaction-params.ts
/**
 * Example: Transaction Parameters
 *
 * This example demonstrates how to get suggested transaction parameters using
 * suggestedParams() and transactionParams() methods. These parameters are essential
 * for constructing valid transactions on the Algorand network.
 *
 * Prerequisites:
 * - LocalNet running (via `algokit localnet start`)
 */


import {
  createAlgodClient,
  printError,
  printHeader,
  printInfo,
  printStep,
  printSuccess,
} from '../shared/utils.js';


/**
 * Format a Uint8Array as base64 string
 */
function formatAsBase64(bytes: Uint8Array): string {
  return Buffer.from(bytes).toString('base64');
}


/**
 * Format a bigint fee as microAlgos and Algos
 */
function formatFee(microAlgos: bigint): string {
  const algoValue = Number(microAlgos) / 1_000_000;
  return `${microAlgos.toLocaleString('en-US')} µALGO (${algoValue.toFixed(6)} ALGO)`;
}


async function main() {
  printHeader('Transaction Parameters Example');


  // Create an Algod client connected to LocalNet
  const algod = createAlgodClient();


  // =========================================================================
  // Step 1: Get Suggested Parameters using suggestedParams()
  // =========================================================================
  printStep(1, 'Getting suggested transaction parameters with suggestedParams()');


  try {
    const suggestedParams = await algod.suggestedParams();


    printSuccess('Suggested parameters retrieved successfully!');
    printInfo('');


    // =========================================================================
    // Step 2: Display Core Parameters
    // =========================================================================
    printStep(2, 'Displaying suggested transaction parameters');


    printInfo('Core Transaction Parameters:');
    printInfo(`  fee:              ${formatFee(suggestedParams.fee)}`);
    printInfo(`  minFee:           ${formatFee(suggestedParams.minFee)}`);
    printInfo(`  flatFee:          ${suggestedParams.flatFee}`);
    printInfo('');


    // =========================================================================
    // Step 3: Display Validity Window Parameters
    // =========================================================================
    printStep(3, 'Displaying validity window parameters (firstRound, lastRound)');


    printInfo('Validity Window:');
    printInfo(`  firstValid:       ${suggestedParams.firstValid.toLocaleString('en-US')}`);
    printInfo(`  lastValid:        ${suggestedParams.lastValid.toLocaleString('en-US')}`);
    printInfo('');


    const validityWindow = suggestedParams.lastValid - suggestedParams.firstValid;
    printInfo(`  Validity Window:  ${validityWindow.toLocaleString('en-US')} rounds`);
    printInfo('The default validity window is 1000 rounds (~1 hour on MainNet)');
    printInfo('A transaction is only valid between firstValid and lastValid rounds');
    printInfo('');


    // =========================================================================
    // Step 4: Display Network Identification Parameters
    // =========================================================================
    printStep(4, 'Displaying network identification parameters');


    printInfo('Network Identification:');
    printInfo(`  genesisId:        ${suggestedParams.genesisId}`);
    printInfo(`  genesisHash:      ${formatAsBase64(suggestedParams.genesisHash)}`);
    printInfo(`  consensusVersion: ${suggestedParams.consensusVersion}`);
    printInfo('');


    printInfo('genesisId and genesisHash uniquely identify the network');
    printInfo('Transactions are rejected if sent to the wrong network');
    printInfo('');


    // =========================================================================
    // Step 5: Explain Each Parameter's Purpose
    // =========================================================================
    printStep(5, "Explaining each parameter's purpose");


    printInfo('Parameter Purposes:');
    printInfo('');
    printInfo('  fee:');
    printInfo('    The suggested fee per byte for the transaction.');
    printInfo('    During network congestion, this value may increase.');
    printInfo('');
    printInfo('  minFee:');
    printInfo('    The minimum fee required regardless of transaction size.');
    printInfo('    Currently 1000 µALGO (0.001 ALGO) on all Algorand networks.');
    printInfo('');
    printInfo('  flatFee:');
    printInfo('    When false, fee is calculated as: fee * transactionSize');
    printInfo('    When true, fee is used directly as the total fee.');
    printInfo('');
    printInfo('  firstValid:');
    printInfo('    The first round this transaction is valid for.');
    printInfo('    Usually set to the current round (lastRound from the node).');
    printInfo('');
    printInfo('  lastValid:');
    printInfo('    The last round this transaction is valid for.');
    printInfo('    Transaction will fail if not confirmed by this round.');
    printInfo('');
    printInfo('  genesisId:');
    printInfo('    A human-readable network identifier (e.g., "mainnet-v1.0").');
    printInfo('    Prevents replaying transactions across networks.');
    printInfo('');
    printInfo('  genesisHash:');
    printInfo('    The SHA256 hash of the genesis block, uniquely identifying the network.');
    printInfo('    Cryptographically ensures transaction is for the correct chain.');
    printInfo('');
    printInfo('  consensusVersion:');
    printInfo('    The consensus protocol version at the current round.');
    printInfo('    Indicates which features and rules are active.');
    printInfo('');


    // =========================================================================
    // Step 6: Demonstrate transactionParams() (alias for suggestedParams)
    // =========================================================================
    printStep(6, 'Demonstrating transactionParams() - alias for suggestedParams()');


    const txnParams = await algod.transactionParams();
    printSuccess('transactionParams() also works and returns the same type!');
    printInfo(`  firstValid:       ${txnParams.firstValid.toLocaleString('en-US')}`);
    printInfo(`  lastValid:        ${txnParams.lastValid.toLocaleString('en-US')}`);
    printInfo('transactionParams() is an alias for suggestedParams() for convenience');
    printInfo('');


    // =========================================================================
    // Step 7: Demonstrate Customizing Parameters
    // =========================================================================
    printStep(7, 'Demonstrating how to customize transaction parameters');


    printInfo('Customizing Parameters:');
    printInfo('');


    // Example 1: Setting a specific flat fee
    const customParams1 = { ...suggestedParams };
    customParams1.flatFee = true;
    customParams1.fee = 2000n; // Set a fixed 2000 µALGO fee


    printInfo('  Example 1: Setting a flat fee');
    printInfo(`    Original fee:   ${formatFee(suggestedParams.fee)}`);
    printInfo(`    Original flatFee: ${suggestedParams.flatFee}`);
    printInfo(`    Custom fee:     ${formatFee(customParams1.fee)}`);
    printInfo(`    Custom flatFee: ${customParams1.flatFee}`);
    printInfo('Set flatFee=true to use a fixed fee instead of per-byte');
    printInfo('');


    // Example 2: Extending the validity window
    const customParams2 = { ...suggestedParams };
    const extendedWindow = 2000n; // 2000 rounds instead of default 1000
    customParams2.lastValid = customParams2.firstValid + extendedWindow;


    printInfo('  Example 2: Extending the validity window');
    printInfo(`    Original lastValid:  ${suggestedParams.lastValid.toLocaleString('en-US')}`);
    printInfo(`    Extended lastValid:  ${customParams2.lastValid.toLocaleString('en-US')}`);
    printInfo(
      `    Original window:     ${(suggestedParams.lastValid - suggestedParams.firstValid).toLocaleString('en-US')} rounds`,
    );
    printInfo(`    Extended window:     ${extendedWindow.toLocaleString('en-US')} rounds`);
    printInfo('Extend validity window for offline signing or delayed submission');
    printInfo('');


    // Example 3: Shortening the validity window
    const customParams3 = { ...suggestedParams };
    const shortWindow = 100n; // Only 100 rounds validity
    customParams3.lastValid = customParams3.firstValid + shortWindow;


    printInfo('  Example 3: Shortening the validity window');
    printInfo(`    Original lastValid:  ${suggestedParams.lastValid.toLocaleString('en-US')}`);
    printInfo(`    Shortened lastValid: ${customParams3.lastValid.toLocaleString('en-US')}`);
    printInfo(`    Shortened window:    ${shortWindow.toLocaleString('en-US')} rounds`);
    printInfo('Shorter windows provide better replay protection');
    printInfo('');


    // Example 4: Setting a specific firstValid for delayed execution
    const customParams4 = { ...suggestedParams };
    const futureRound = suggestedParams.firstValid + 10n; // Valid starting 10 rounds from now
    customParams4.firstValid = futureRound;
    customParams4.lastValid = futureRound + 1000n;


    printInfo('  Example 4: Delayed execution (future firstValid)');
    printInfo(`    Original firstValid: ${suggestedParams.firstValid.toLocaleString('en-US')}`);
    printInfo(`    Delayed firstValid:  ${customParams4.firstValid.toLocaleString('en-US')}`);
    printInfo(`    Delayed lastValid:   ${customParams4.lastValid.toLocaleString('en-US')}`);
    printInfo('Set future firstValid to prevent immediate execution');
  } catch (error) {
    printError(
      `Failed to get transaction parameters: ${error instanceof Error ? error.message : String(error)}`,
    );
    printInfo('Make sure LocalNet is running with `algokit localnet start`');
    process.exit(1);
  }


  // =========================================================================
  // Summary
  // =========================================================================
  printHeader('Summary');
  printInfo('This example demonstrated:');
  printInfo('  1. suggestedParams() - Get parameters for building transactions');
  printInfo('  2. Parameter fields: fee, minFee, flatFee, firstValid, lastValid');
  printInfo('  3. Network identification: genesisId, genesisHash, consensusVersion');
  printInfo('  4. How firstValid and lastValid define the validity window');
  printInfo('  5. transactionParams() - Alias for suggestedParams()');
  printInfo('  6. Customizing parameters: fees and validity windows');
  printInfo('');
  printInfo('Key SuggestedParams fields:');
  printInfo('  - fee: Suggested fee per byte (bigint)');
  printInfo('  - minFee: Minimum transaction fee (bigint)');
  printInfo('  - flatFee: Whether fee is flat or per-byte (boolean)');
  printInfo('  - firstValid: First valid round (bigint)');
  printInfo('  - lastValid: Last valid round (bigint)');
  printInfo('  - genesisId: Network identifier string');
  printInfo('  - genesisHash: Genesis block hash (Uint8Array)');
  printInfo('  - consensusVersion: Protocol version string');
  printInfo('');
  printInfo('Use cases:');
  printInfo('  - Building transactions with correct fees');
  printInfo('  - Setting appropriate validity windows');
  printInfo('  - Ensuring network compatibility');
  printInfo('  - Offline transaction signing with extended windows');
}


main().catch(error => {
  console.error('Fatal error:', error);
  process.exit(1);
});

Other examples in Algod Client

Section titled “Other examples in Algod Client”