eth_maxPriorityFeePerGas | Unichain RPC Docs

Get the suggested priority fee (tip) per gas for EIP-1559 transactions on Unichain. Essential for gas estimation, fee optimization, and time-sensitive transaction pricing.

Returns the current suggested priority fee (tip) per gas in wei on Unichain. This is the amount paid directly to validators to incentivize faster transaction inclusion in EIP-1559 compatible blocks.

Why Unichain? Build on Uniswap's DeFi-optimized Superchain L2 with 250ms sub-blocks and 95% lower costs than Ethereum with 250ms sub-blocks (fastest L2), TEE-secured block building, native Superchain interoperability, and 65% revenue to validators.

When to Use This Method

eth_maxPriorityFeePerGas is essential for DeFi developers, liquidity protocol builders, and teams building on the Optimism Superchain:

EIP-1559 Transaction Building — Get the recommended tip to include in maxPriorityFeePerGas when constructing type-2 transactions on Unichain
Fee Optimization — Balance transaction speed against cost by adjusting the priority fee relative to the suggested value
Time-Sensitive Transactions — Increase the tip above the suggested value for DEX swaps, liquidations, or other latency-sensitive operations on decentralized exchanges, liquidity protocols, and MEV-protected DeFi applications
Gas Price Estimation — Combine with baseFeePerGas from the latest block to calculate the total maxFeePerGas for accurate fee estimation

import { JsonRpcProvider, Wallet, parseEther } from 'ethers';

const provider = new JsonRpcProvider('https://api-unichain-mainnet.n.dwellir.com/YOUR_API_KEY');

async function buildEIP1559Transaction(privateKey, to, valueEth) {
  const wallet = new Wallet(privateKey, provider);

  // Get current fee data
  const feeData = await provider.getFeeData();
  const latestBlock = await provider.getBlock('latest');
  const baseFee = latestBlock.baseFeePerGas;

  // Set maxPriorityFeePerGas from the suggestion
  const maxPriorityFeePerGas = feeData.maxPriorityFeePerGas;

  // maxFeePerGas = 2 * baseFee + maxPriorityFeePerGas (buffer for base fee increases)
  const maxFeePerGas = baseFee * 2n + maxPriorityFeePerGas;

  const tx = await wallet.sendTransaction({
    to,
    value: parseEther(valueEth),
    type: 2,
    maxPriorityFeePerGas,
    maxFeePerGas
  });

  console.log('Sent with priority fee:', Number(maxPriorityFeePerGas) / 1e9, 'Gwei');
  return tx;
}

2. Dynamic Fee Strategy

Adjust priority fees based on transaction urgency:

JavaScript

async function getFeeByUrgency(provider, urgency = 'standard') {
  const feeData = await provider.getFeeData();
  const basePriorityFee = feeData.maxPriorityFeePerGas;

  const multipliers = {
    low: 0.8,       // Willing to wait
    standard: 1.0,  // Normal speed
    fast: 1.5,      // Faster inclusion
    urgent: 2.0     // Next-block target
  };

  const multiplier = multipliers[urgency] || 1.0;
  const adjustedFee = BigInt(Math.ceil(Number(basePriorityFee) * multiplier));

  const block = await provider.getBlock('latest');
  const maxFeePerGas = block.baseFeePerGas * 2n + adjustedFee;

  return {
    maxPriorityFeePerGas: adjustedFee,
    maxFeePerGas
  };
}

// Usage
const fees = await getFeeByUrgency(provider, 'fast');
console.log('Priority fee:', Number(fees.maxPriorityFeePerGas) / 1e9, 'Gwei');
console.log('Max fee:', Number(fees.maxFeePerGas) / 1e9, 'Gwei');

3. Priority Fee Monitor

Track priority fee changes over time on Unichain:

JavaScript

async function monitorPriorityFee(provider, interval = 12000) {
  let previousFee = null;

  setInterval(async () => {
    const feeData = await provider.getFeeData();
    const currentFee = feeData.maxPriorityFeePerGas;
    const feeGwei = Number(currentFee) / 1e9;

    if (previousFee !== null) {
      const change = Number(currentFee - previousFee) / Number(previousFee) * 100;
      const direction = change > 0 ? 'UP' : change < 0 ? 'DOWN' : 'STABLE';
      console.log(`Priority fee: ${feeGwei.toFixed(4)} Gwei (${direction} ${Math.abs(change).toFixed(1)}%)`);
    } else {
      console.log(`Priority fee: ${feeGwei.toFixed(4)} Gwei`);
    }

    previousFee = currentFee;
  }, interval);
}

Error Handling

Common errors and solutions:

Error Code	Description	Solution
-32601	Method not found	The node may not support EIP-1559 — fall back to `eth_gasPrice`
-32603	Internal error	Retry with exponential backoff
-32005	Rate limit exceeded	Implement rate limiting and caching client-side

JavaScript

async function getSafePriorityFee(provider, maxRetries = 3) {
  for (let i = 0; i < maxRetries; i++) {
    try {
      const feeData = await provider.getFeeData();
      if (feeData.maxPriorityFeePerGas !== null) {
        return feeData.maxPriorityFeePerGas;
      }
      // Fallback: derive from legacy gas price
      const gasPrice = await provider.send('eth_gasPrice', []);
      return BigInt(gasPrice);
    } catch (error) {
      if (error.code === -32601) {
        // EIP-1559 not supported — use legacy gas price
        const gasPrice = await provider.send('eth_gasPrice', []);
        return BigInt(gasPrice);
      }
      if (i === maxRetries - 1) throw error;
      await new Promise(r => setTimeout(r, Math.pow(2, i) * 1000));
    }
  }
}

eth_gasPrice — Get the legacy gas price
eth_feeHistory — Get historical fee data for trend analysis
eth_estimateGas — Estimate gas units required for a transaction
eth_getBlockByNumber — Get block details including baseFeePerGas

eth_maxPriorityFeePerGas - Unichain RPC Method

When to Use This Method

Code Examples

Common Use Cases

1. Build an EIP-1559 Transaction

2. Dynamic Fee Strategy

3. Priority Fee Monitor

Error Handling

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