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Overview

Monei integrates with leading DEX aggregators to provide the best swap rates across multiple decentralized exchanges. This guide covers token swaps on EVM networks. What you’ll learn:
  • Get swap quotes and rates
  • Swap native tokens to ERC-20 tokens
  • Swap ERC-20 to ERC-20 tokens
  • Swap ERC-20 tokens back to native
  • Price impact and slippage
  • Gas optimization for swaps

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Swap Types

Native → Token

Swap ETH/BNB/MATIC to any ERC-20 token

Token → Token

Swap between any two ERC-20 tokens

Token → Native

Swap ERC-20 tokens back to native currency

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Get Swap Quote

Always get a quote before executing a swap to see the exchange rate and estimated output.

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Native to Token Quote

import MoneiSDK from 'monei-sdk';

const monei = new MoneiSDK({
  apiKey: process.env.MONEI_API_KEY,
});

// Get quote for swapping 0.1 BNB to USDT on BSC
const quote = await monei.evmExchange.getQuoteNativeToToken({
  outputMint: '0x55d398326f99059fF775485246999027B3197955', // USDT on BSC
  amount: '0.1', // 0.1 BNB
  chainId: 56
});

console.log('Quote ID:', quote.quoteId);
console.log('From:', quote.fromToken.symbol, '(Native)');
console.log('To:', quote.toToken.symbol);
console.log('Input Amount:', quote.fromAmount);
console.log('Output Amount:', quote.toAmount);
console.log('Exchange Rate:', quote.rate);
console.log('Minimum Output:', quote.minToAmount, '(with slippage)');
console.log('Price Impact:', quote.priceImpact + '%');
console.log('Gas Cost:', quote.estimatedGasUsd, 'USD');
console.log('Expires At:', new Date(quote.expiryTimestamp * 1000));
Response: 
{
  "statusCode": 200,
  "message": "Quote retrieved successfully",
  "data": {
    "quoteId": "0x592dbadfad19da6808b637c2",
    "fromToken": {
      "address": null,
      "symbol": "BNB",
      "decimals": 18
    },
    "toToken": {
      "address": "0x55d398326f99059fF775485246999027B3197955",
      "symbol": "USDT",
      "decimals": 18
    },
    "fromAmount": "100000000000000000",
    "toAmount": "28700000000000000000",
    "rate": "287.0",
    "reverseRate": "0.003484",
    "minToAmount": "28413000000000000000",
    "protocolFee": "100000000000000",
    "protocolFeeToken": {
      "address": null,
      "symbol": "BNB",
      "decimals": 18
    },
    "estimatedGas": "150000",
    "estimatedGasUsd": "1.25",
    "priceImpact": "0.15",
    "liquidityAvailable": true,
    "totalValueUsd": "28.70",
    "expiryTimestamp": 1698765432,
    "blockNumber": "24161093",
    "chainId": 56
  }
}

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Token to Token Quote

// Get quote for USDT → USDC swap on BSC
const quote = await monei.evmExchange.getQuoteTokenToToken({
  inputMint: '0x55d398326f99059fF775485246999027B3197955', // USDT
  outputMint: '0x8AC76a51cc950d9822D68b83fE1Ad97B32Cd580d', // USDC
  amount: '100', // 100 USDT
  chainId: 56
});

console.log('Swap 100 USDT → USDC');
console.log('Rate:', quote.rate);
console.log('Output:', quote.toAmount, 'USDC');
console.log('Min Output:', quote.minToAmount, 'USDC');
console.log('Price Impact:', quote.priceImpact + '%');

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Token to Native Quote

// Get quote for USDT → BNB swap
const quote = await monei.evmExchange.getQuoteTokenToNative({
  inputMint: '0x55d398326f99059fF775485246999027B3197955', // USDT
  amount: '100', // 100 USDT
  chainId: 56
});

console.log('Swap 100 USDT → BNB');
console.log('Rate:', quote.rate);
console.log('Output:', quote.toAmount, 'BNB');
console.log('Min Output:', quote.minToAmount, 'BNB');

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Execute Swap

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Swap Native to Token

// Swap 0.1 BNB to USDT on BSC
const swap = await monei.evmExchange.swapNativeToToken({
  outputMint: '0x55d398326f99059fF775485246999027B3197955', // USDT
  amount: '0.1', // 0.1 BNB
  amountOut: '28', // Expected minimum USDT output
  chainId: 56
});

console.log('Transaction Hash:', swap.txHash);
console.log('View on BscScan:', `https://bscscan.com/tx/${swap.txHash}`);

// Wait for confirmation
await monei.evm.waitForTransaction(swap.txHash, 56);
console.log('Swap completed!');
Response: 
{
  "statusCode": 200,
  "message": "Swap executed successfully",
  "data": {
    "txHash": "0x1234567890abcdef1234567890abcdef1234567890abcdef1234567890abcdef"
  }
}

​
Swap Token to Token

// Swap 100 USDT to USDC on BSC
const swap = await monei.evmExchange.swapTokenToToken({
  inputMint: '0x55d398326f99059fF775485246999027B3197955', // USDT
  outputMint: '0x8AC76a51cc950d9822D68b83fE1Ad97B32Cd580d', // USDC
  amount: '100',
  chainId: 56
});

console.log('Transaction Hash:', swap.txHash);
console.log('View on BscScan:', `https://bscscan.com/tx/${swap.txHash}`);

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Swap Token to Native

// Swap 100 USDT to BNB on BSC
const swap = await monei.evmExchange.swapTokenToNative({
  inputMint: '0x55d398326f99059fF775485246999027B3197955', // USDT
  amount: '100',
  chainId: 56
});

console.log('Transaction Hash:', swap.txHash);
console.log('View on BscScan:', `https://bscscan.com/tx/${swap.txHash}`);

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Understanding Quote Details

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Key Quote Fields

FieldDescription
quoteIdUnique identifier for this quote (valid for ~5 minutes)
rateExchange rate (1 input token = X output tokens)
reverseRateReverse rate (1 output token = Y input tokens)
toAmountExpected output amount
minToAmountMinimum output after slippage (usually 0.5%)
priceImpactHow much this trade affects the market price
estimatedGasEstimated gas cost in native token
estimatedGasUsdEstimated gas cost in USD
liquidityAvailableWhether sufficient liquidity exists
expiryTimestampWhen this quote expires (Unix timestamp)

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Price Impact

Price impact shows how much your trade will move the market price:
Price ImpactInterpretationAction
< 1%Low impactSafe to proceed
1% - 3%Moderate impactConsider splitting trade
3% - 5%High impactWarning recommended
> 5%Very high impactSplit into smaller trades
// Check price impact before swapping
const quote = await monei.evmExchange.getQuoteNativeToToken({
  outputMint: tokenAddress,
  amount: '1.0',
  chainId: 56
});

const priceImpact = parseFloat(quote.priceImpact);

if (priceImpact > 5) {
  console.log('⚠️ WARNING: Very high price impact!');
  console.log('Consider splitting into smaller trades');
} else if (priceImpact > 3) {
  console.log('⚠️ High price impact:', priceImpact + '%');
} else if (priceImpact > 1) {
  console.log('ℹ️ Moderate price impact:', priceImpact + '%');
} else {
  console.log('✓ Low price impact:', priceImpact + '%');
}

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Slippage Protection

Slippage is the difference between expected and actual output amounts. Default Slippage: 0.5% (configurable) 
// Calculate minimum output with custom slippage
function calculateMinOutput(expectedOutput, slippagePercent = 0.5) {
  const slippage = 1 - (slippagePercent / 100);
  return (parseFloat(expectedOutput) * slippage).toFixed(6);
}

// Get quote
const quote = await monei.evmExchange.getQuoteNativeToToken({
  outputMint: tokenAddress,
  amount: '0.1',
  chainId: 56
});

// Calculate min output with 1% slippage
const minOutput = calculateMinOutput(quote.toAmount, 1.0);

console.log('Expected Output:', quote.toAmount);
console.log('Min Output (1% slippage):', minOutput);
console.log('Default Min Output (0.5%):', quote.minToAmount);

// Execute with custom slippage
const swap = await monei.evmExchange.swapNativeToToken({
  outputMint: tokenAddress,
  amount: '0.1',
  amountOut: minOutput, // Custom min output
  chainId: 56
});
Recommended Slippage:
Market ConditionRecommended Slippage
Stablecoin swaps0.1% - 0.3%
Normal volatility0.5% - 1.0%
High volatility1.0% - 3.0%
Very low liquidity3.0% - 5.0%

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Gas Optimization

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Network Comparison for Swaps

NetworkTypical Swap GasUSD CostBest For
Polygon~200,000 gas0.05−0.05 - 0.20Small/frequent swaps
BSC~180,000 gas0.50−0.50 - 2.00Medium swaps
Base~150,000 gas1.00−1.00 - 3.00Fast execution
Arbitrum~200,000 gas1.00−1.00 - 5.00Balanced cost/speed
Optimism~200,000 gas0.50−0.50 - 3.00L2 efficiency
Ethereum~150,000 gas30−30 - 100Large swaps only

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Optimize Swap Costs

// Compare costs across networks
async function findBestNetwork(tokenInAddress, tokenOutAddress, amount) {
  const networks = [
    { chainId: 56, name: 'BSC' },
    { chainId: 137, name: 'Polygon' },
    { chainId: 8453, name: 'Base' },
    { chainId: 42161, name: 'Arbitrum' }
  ];
  
  const quotes = [];
  
  for (const network of networks) {
    try {
      const quote = await monei.evmExchange.getQuoteTokenToToken({
        inputMint: tokenInAddress,
        outputMint: tokenOutAddress,
        amount: amount,
        chainId: network.chainId
      });
      
      quotes.push({
        network: network.name,
        chainId: network.chainId,
        output: quote.toAmount,
        gasCostUsd: parseFloat(quote.estimatedGasUsd),
        netOutput: parseFloat(quote.toAmount) - parseFloat(quote.estimatedGasUsd)
      });
    } catch (error) {
      console.log(`${network.name}: Token not available`);
    }
  }
  
  // Sort by net output (after gas)
  quotes.sort((a, b) => b.netOutput - a.netOutput);
  
  console.log('\nNetwork Comparison:');
  quotes.forEach(q => {
    console.log(`${q.network}:`);
    console.log(`  Output: ${q.output}`);
    console.log(`  Gas Cost: $${q.gasCostUsd}`);
    console.log(`  Net: ${q.netOutput}`);
  });
  
  return quotes[0]; // Best network
}

// Find best network for swap
const best = await findBestNetwork(usdtAddress, usdcAddress, '100');
console.log(`\nBest Network: ${best.network}`);

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Common Token Pairs

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Stablecoin Swaps (BSC)

// USDT to USDC
const swap = await monei.evmExchange.swapTokenToToken({
  inputMint: '0x55d398326f99059fF775485246999027B3197955', // USDT
  outputMint: '0x8AC76a51cc950d9822D68b83fE1Ad97B32Cd580d', // USDC
  amount: '1000',
  chainId: 56
});

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Best Practices

Always Get Quote

Get fresh quote before each swap (quotes expire in ~5 min)

Check Price Impact

Avoid swaps with high price impact (>5%)

Set Slippage

Use appropriate slippage for market conditions

Monitor Gas

Factor gas costs into swap profitability

Use Cheap Networks

Polygon/BSC for small swaps, Ethereum for large

Test Small First

Test with small amount before large swaps

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Troubleshooting

Error: Transaction reverted due to slippageCause: Actual output fell below minimum due to price movementSolution:
  • Increase slippage tolerance
  • Get fresh quote
  • Split into smaller trades
  • Try during less volatile periods
Error: Not enough liquidity for swapSolutions:
  • Reduce swap amount
  • Try different network
  • Use more liquid token pairs (USDT/USDC)
  • Check DEX liquidity on explorer
Error: Quote ID expired or invalidCause: Quotes are valid for ~5 minutesSolution:
  • Get fresh quote before swapping
  • Execute swap immediately after quote
  • Don’t reuse old quotes
Warning: Price impact > 5%Recommendations:
  • Split into multiple smaller swaps
  • Use different network with more liquidity
  • Wait for better liquidity
  • Consider limit orders (if available)

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Next Steps

Wallet Operations

Manage your EVM wallet

Transactions

Learn about EVM transactions

Solana Swaps

Swap tokens on Solana

Networks

Explore supported networks