EIP-1559 Transactions

Dynamic fee market transactions (Type 2)

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Run Transaction examples in the interactive playground

EIP-1559 Transactions

Dynamic fee market transactions with base fee and priority fee, introduced in London hard fork.

Overview

EIP-1559 transactions (Type 2) replace fixed gas price with dynamic fee market. Users specify maxFeePerGas and maxPriorityFeePerGas, with actual fee determined by block’s base fee.

Type Definition

type EIP1559 = {
  type: Type.EIP1559      // 0x02
  chainId: bigint
  nonce: bigint
  maxPriorityFeePerGas: bigint  // Tip to miner
  maxFeePerGas: bigint          // Maximum total fee
  gasLimit: bigint
  to: AddressType | null
  value: bigint
  data: Uint8Array
  accessList: AccessList
  yParity: number         // 0 or 1
  r: Uint8Array           // 32 bytes
  s: Uint8Array           // 32 bytes
}

Source: types.ts:92-109

Creating EIP-1559 Transactions

import * as Transaction from 'tevm/Transaction'

const tx: Transaction.EIP1559 = {
  type: Transaction.Type.EIP1559,
  chainId: 1n,
  nonce: 0n,
  maxPriorityFeePerGas: 2000000000n,  // 2 gwei tip
  maxFeePerGas: 30000000000n,         // 30 gwei max
  gasLimit: 21000n,
  to: recipientAddress,
  value: 1000000000000000000n,  // 1 ETH
  data: new Uint8Array(),
  accessList: [],
  yParity: 0,
  r: signatureR,
  s: signatureS,
}

Fee Market Mechanics

Base Fee

Block base fee adjusts based on block fullness:

• Block > 50% full: base fee increases
• Block < 50% full: base fee decreases
• Maximum 12.5% change per block

Effective Gas Price

effectiveGasPrice = baseFee + min(maxPriorityFeePerGas, maxFeePerGas - baseFee)

Examples:

// Case 1: Normal case
baseFee = 15 gwei
maxPriorityFeePerGas = 2 gwei
maxFeePerGas = 30 gwei
// effectiveGasPrice = 15 + min(2, 30 - 15) = 15 + 2 = 17 gwei

// Case 2: maxFeePerGas too low
baseFee = 15 gwei
maxPriorityFeePerGas = 5 gwei
maxFeePerGas = 18 gwei
// effectiveGasPrice = 15 + min(5, 18 - 15) = 15 + 3 = 18 gwei

// Case 3: maxFeePerGas = baseFee
baseFee = 20 gwei
maxPriorityFeePerGas = 2 gwei
maxFeePerGas = 20 gwei
// effectiveGasPrice = 20 + min(2, 20 - 20) = 20 + 0 = 20 gwei

getEffectiveGasPrice

Calculate effective gas price given base fee.

function getEffectiveGasPrice(
  tx: BrandedTransactionEIP1559,
  baseFee: bigint
): bigint

Usage

import { EIP1559 } from 'tevm/Transaction'

const tx: Transaction.EIP1559 = {
  maxPriorityFeePerGas: 2000000000n,
  maxFeePerGas: 30000000000n,
  // ...
}

const baseFee = 15000000000n  // From block header
const effectivePrice = EIP1559.getEffectiveGasPrice(tx, baseFee)
console.log(effectivePrice)  // 17000000000n (17 gwei)

// Total cost
const totalCost = effectivePrice * gasUsed + tx.value

Source: EIP1559/getEffectiveGasPrice.js:13-18

Fee Estimation

Setting maxFeePerGas

Rule of thumb: maxFeePerGas = baseFee * 2 + maxPriorityFeePerGas

async function estimateFees(provider) {
  const block = await provider.getBlock('latest')
  const baseFee = block.baseFeePerGas

  return {
    maxFeePerGas: baseFee * 2n + 2000000000n,
    maxPriorityFeePerGas: 2000000000n  // 2 gwei tip
  }
}

Aggressive vs Conservative

// Aggressive (fast inclusion)
const aggressive = {
  maxPriorityFeePerGas: 3000000000n,  // 3 gwei
  maxFeePerGas: baseFee * 2n + 3000000000n
}

// Conservative (cheaper, slower)
const conservative = {
  maxPriorityFeePerGas: 1000000000n,  // 1 gwei
  maxFeePerGas: baseFee + 5000000000n  // baseFee + 5 gwei buffer
}

Gas Cost Calculation

// Maximum possible cost
const maxCost = tx.maxFeePerGas * tx.gasLimit + tx.value

// Actual cost (after execution)
const actualCost = effectiveGasPrice * gasUsed + tx.value

// Refund
const refund = (tx.maxFeePerGas - effectiveGasPrice) * gasUsed

RLP Encoding

0x02 || rlp([chainId, nonce, maxPriorityFeePerGas, maxFeePerGas, gasLimit, to, value, data, accessList, yParity, r, s])

Methods

import { EIP1559 } from 'tevm/Transaction'

// Serialization
const bytes = EIP1559.serialize(eip1559Tx)
const decoded = EIP1559.deserialize(bytes)

// Hashing
const txHash = EIP1559.hash(eip1559Tx)
const signingHash = EIP1559.getSigningHash(eip1559Tx)

// Signing
const sender = EIP1559.getSender(eip1559Tx)
const isValid = EIP1559.verifySignature(eip1559Tx)

// Gas price
const effectivePrice = EIP1559.getEffectiveGasPrice(eip1559Tx, baseFee)

Benefits

1. Predictable pricing - Base fee makes fees more predictable
2. Better UX - Users specify maximum, pay actual
3. Faster confirmation - Priority fee for faster inclusion
4. ETH burn - Base fee burned, reduces ETH supply
5. Less overpaying - Only pay what’s needed

When to Use

Use EIP-1559 for:

• Ethereum mainnet (London+)
• Modern L2s with EIP-1559 support
• Applications needing predictable fees

Prefer Legacy/EIP-2930 for:

• Networks without EIP-1559
• Specific gas price requirements

EIP Reference

• EIP-1559: Fee market change for ETH 1.0 chain