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> Fetch the complete documentation index at: https://voltaire.tevm.sh/llms.txt
> Use this file to discover all available pages before exploring further.

# Hardfork.hasEIP1559

> Check if EIP-1559 base fee mechanism is available

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## EIP-1559 Features

**Active Since:** London (August 5, 2021)

### Changes Introduced

**Base Fee Mechanism:**

* Base fee per gas (burned, not paid to miners)
* Dynamic base fee adjustment based on block fullness
* Target block utilization: 50% (15M gas out of 30M limit)
* Base fee increases/decreases by max 12.5% per block

**Transaction Format:**

* Type 2 transactions (EIP-1559 format)
* `maxFeePerGas` - Maximum total fee willing to pay
* `maxPriorityFeePerGas` - Tip for block producer
* Effective gas price = `min(maxFeePerGas, baseFee + maxPriorityFeePerGas)`

**New Opcode:**

* `BASEFEE` (0x48) - Pushes current block's base fee onto stack

## Usage Patterns

### Transaction Type Selection

Choose appropriate transaction format:

```typescript theme={null}
import { Hardfork } from 'tevm'

function buildTransaction(fork: BrandedHardfork, params: TxParams) {
  if (fork.hasEIP1559()) {
    return {
      type: 2,  // EIP-1559
      maxFeePerGas: params.maxFee,
      maxPriorityFeePerGas: params.tip
    }
  }

  return {
    type: 0,  // Legacy
    gasPrice: params.gasPrice
  }
}
```

### Gas Price Calculation

Calculate effective gas price:

```typescript theme={null}
import { Hardfork } from 'tevm'

function calculateGasPrice(
  fork: BrandedHardfork,
  baseFee: bigint,
  maxPriorityFee: bigint
): bigint {
  if (fork.hasEIP1559()) {
    return baseFee + maxPriorityFee
  }

  // Pre-EIP-1559: fixed gas price
  return baseFee
}
```

### Fee Market Configuration

Configure fee market parameters:

```typescript theme={null}
import { Hardfork } from 'tevm'

function getFeeMarketConfig(fork: BrandedHardfork) {
  if (fork.hasEIP1559()) {
    return {
      baseFeeChangeDenominator: 8,      // 12.5% max change
      elasticityMultiplier: 2,          // 2x target gas limit
      baseFeeMaxChangeDenominator: 8
    }
  }

  return null  // No dynamic base fee
}
```

### Opcode Availability

Check BASEFEE opcode support:

```typescript theme={null}
import { Hardfork } from 'tevm'

function getBaseFeeOpcode(fork: BrandedHardfork): number | null {
  if (fork.hasEIP1559()) {
    return 0x48  // BASEFEE opcode
  }

  return null  // Not available
}
```

## Network Configuration

Validate network supports EIP-1559:

```typescript theme={null}
import { Hardfork, LONDON } from 'tevm'

function validateEIP1559Support(config: NetworkConfig) {
  const fork = Hardfork(config.hardfork)

  if (!fork.hasEIP1559()) {
    throw new Error(
      `Network ${config.name} does not support EIP-1559. ` +
      `Requires London or later, got ${Hardfork.toString(fork)}`
    )
  }
}
```

## EIP References

**Primary:**

* [EIP-1559](https://eips.ethereum.org/EIPS/eip-1559) - Fee market change for ETH 1.0 chain

**Related:**

* [EIP-3198](https://eips.ethereum.org/EIPS/eip-3198) - BASEFEE opcode
* [EIP-2718](https://eips.ethereum.org/EIPS/eip-2718) - Typed transaction envelope (required for Type 2)

## Impact

**For Users:**

* More predictable transaction fees
* No overpaying during low-congestion periods
* Base fee burned (deflationary pressure on ETH)

**For Developers:**

* Must handle two transaction formats (Type 0 legacy, Type 2 EIP-1559)
* Fee estimation more complex (base fee + priority fee)
* BASEFEE opcode available for smart contracts

**For Validators:**

* Only receive priority fee (tip), not base fee
* Incentivized to include transactions with higher tips

## See Also

* [hasEIP3855](/primitives/hardfork/has-eip3855) - Check PUSH0 opcode availability (Shanghai)
* [hasEIP4844](/primitives/hardfork/has-eip4844) - Check blob transactions availability (Cancun)
* [isAtLeast](/primitives/hardfork/is-at-least) - General version comparison