> ## Documentation Index
> Fetch the complete documentation index at: https://optimism-373f39ad-soyboy-docs-op-supernode-guide.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# Transaction Fees 101

> How to check and tune the fee parameters on your OP Stack chain, with example scenarios for common situations.

This guide shows how to check and adjust the fee-related parameters on your chain's `SystemConfig` contract, and when each adjustment makes sense. It applies to the Jovian and following hardforks.

* For how each fee component is calculated, see [transaction fees on OP Mainnet](https://docs.optimism.io/op-stack/transactions/fees#transaction-fees-on-op-mainnet).
* For the full parameter catalogue — types, setters, and the OP Mainnet values — see the [fee parameters reference](/chain-operators/reference/fee-parameters).

On an OP Stack chain a transaction's **Total Fee** is made of three main components:

`Total Fee = L2 Fee + L1 Fee + Operator Fee`

Fees are gathered in dedicated contract [fee vaults](/op-stack/transactions/fee-vaults) that collect the different fee components (for example `BaseFeeVault`, `SequencerFeeVault`, etc.). See the [fee vault operations guide](/chain-operators/guides/management/fee-vaults) for how to manage and withdraw from these vaults.

## Before you start

<Info>
  Only the [SystemConfig owner](/op-stack/protocol/privileged-roles) can change these parameters.
</Info>

Export the values used by all the commands below:

```bash theme={null}
export L1_RPC=<L1_RPC>
export SYSTEM_CONFIG=<SYSTEM_CONFIG_ADDRESS>
export PK=<SYSTEM_CONFIG_OWNER_PRIVATE_KEY>
```

## Tune the L2 fee

The L2 fee is the EVM execution cost: `gasUsed * (baseFee + priorityFee)`. The `baseFee` is computed with the EIP-1559 mechanism and is **collected in the BaseFeeVault (not burned)** on OP Stack.

You can tune L2 fee dynamics on the SystemConfig via:

* `eip1559Denominator`: EIP-1559 max-change denominator, it appears in the denominator of the per-block base fee delta. Lower = faster response, so base fee adjusts faster but results in more volatility.
* `eip1559Elasticity`: elasticity multiplier, sets the target relative to gasLimit. As `gas_target = gasLimit / elasticity`, a **smaller gas target** (larger elasticity) means the base fee will start increasing at a lower block gas usage (i.e., base fee increases sooner under load).
* `gasLimit`: max gas per block. Lower `gasLimit` = less available gas per block (less supply), which makes base fees more sensitive to demand and can cause the base fee to move more easily.
* `minBaseFee`: minimum floor on base fee, in wei (it can be 0). See [setting the minimum base fee](/chain-operators/guides/features/setting-min-base-fee).

### Check current values

```bash theme={null}
cast call --rpc-url $L1_RPC $SYSTEM_CONFIG "eip1559Denominator()"
cast call --rpc-url $L1_RPC $SYSTEM_CONFIG "eip1559Elasticity()"
cast call --rpc-url $L1_RPC $SYSTEM_CONFIG "minBaseFee()"
cast call --rpc-url $L1_RPC $SYSTEM_CONFIG "gasLimit()"
```

### Set values

```bash theme={null}
cast send --rpc-url $L1_RPC --private-key $PK \
  $SYSTEM_CONFIG "setEIP1559Params(uint32,uint32)" <denominator> <elasticity>
cast send --rpc-url $L1_RPC --private-key $PK \
  $SYSTEM_CONFIG "setMinBaseFee(uint64)" <minBaseFeeWei>
cast send --rpc-url $L1_RPC --private-key $PK \
  $SYSTEM_CONFIG "setGasLimit(uint64)" <gasLimit>
```

## Tune the L1 fee

The L1 fee charges for posting L2 data to L1: the transaction's estimated compressed (FastLZ) size is multiplied by a scalar-weighted L1 price. See the [fee parameters reference](/chain-operators/reference/fee-parameters#fee-formulas) for the formula.

Reasons to tweak it:

* Modify margin charged on top of expected costs
* Adjust FastLZ estimates to reflect costs
* Differentiate charges for per-byte vs per-blob costs to reflect actual L1 pricing

The knobs:

* `basefeeScalar`: scales the `l1BaseFee` contribution to the L1 data fee (per-byte).
* `blobBaseFeeScalar`: scales the `l1BlobBaseFee` contribution (per-blob).

### Check current values

```bash theme={null}
cast call --rpc-url $L1_RPC $SYSTEM_CONFIG "basefeeScalar()"
cast call --rpc-url $L1_RPC $SYSTEM_CONFIG "blobbasefeeScalar()"
```

### Set values

```bash theme={null}
cast send --rpc-url $L1_RPC --private-key $PK \
  $SYSTEM_CONFIG "setGasConfigEcotone(uint32,uint32)" <basefeeScalar> <blobBaseFeeScalar>
```

## Tune the operator fee

The operator fee is a discretionary, non-standard fee charged per transaction: `(gasUsed * operatorFeeScalar * 100) + operatorFeeConstant`. See [setting the operator fee](/chain-operators/guides/features/setting-operator-fee) for a dedicated guide.

* `operatorFeeScalar`: per-gas operator margin.
* `operatorFeeConstant`: flat per-transaction operator fee, in wei.

<Warning>
  Any non-zero operator fee makes the chain configuration [non-standard](/chain-operators/reference/standard-configuration).
</Warning>

### Check current values

```bash theme={null}
cast call --rpc-url $L1_RPC $SYSTEM_CONFIG "operatorFeeScalar()"
cast call --rpc-url $L1_RPC $SYSTEM_CONFIG "operatorFeeConstant()"
```

### Set values

```bash theme={null}
cast send --rpc-url $L1_RPC --private-key $PK \
  $SYSTEM_CONFIG "setOperatorFeeScalars(uint32,uint64)" <operatorFeeScalar> <operatorFeeConstant>
```

## Tune the DA footprint limit

The `daFootprintGasScalar` is an in-protocol limit on estimated DA usage to prevent DA spam and priority fee auctions. See [how the DA footprint block limit works](/chain-operators/reference/da-footprint) for the concept and the [DA footprint setup guide](/chain-operators/guides/features/setting-da-footprint) for a dedicated walkthrough.

* Default value is **400**
* A value of **0** is treated as **400**
* Setting it to **1** effectively disables DA footprint limiting

### Check current value

```bash theme={null}
cast call --rpc-url $L1_RPC $SYSTEM_CONFIG "daFootprintGasScalar()"
```

### Set value

```bash theme={null}
cast send --rpc-url $L1_RPC --private-key $PK \
  $SYSTEM_CONFIG "setDAFootprintGasScalar(uint16)" <daFootprintGasScalar>
```

## Example scenarios

### Normal traffic / below EIP-1559 target

**What you'll see**

* If blocks stay below the EIP-1559 target, `baseFee` trends toward the `minBaseFee` floor.
* When L1 data usage is low, the L2 execution fee (`gasUsed * (baseFee + priorityFee)`) is typically the largest cost component.
* The L1 data fee remains low/steady if calldata per transaction is small.

**What to tweak**

* Usually nothing.
* If you need a revenue floor set/increase `minBaseFee`.

**Tradeoff**

* **Pros:** `minBaseFee` prevents prolonged low base fees and provides a predictable minimum (can be left at 0 to improve UX).
* **Cons:** If set too high, it raises inclusion cost for low-value transactions and can negatively impact UX/accessibility.

***

### Busy blocks / congestion

**What you'll see**

* `baseFee` rises when blocks exceed the target: `gas_target = gasLimit / eip1559Elasticity`
* Transactions with low priority tips may experience slower inclusion during congestion.

**What to tweak**

* `eip1559Elasticity` and `eip1559Denominator` :
  * To increase responsiveness: decrease `eip1559Denominator` and/or increase `eip1559Elasticity` (smaller target → baseFee increases sooner).
  * To decrease volatility: increase `eip1559Denominator` and/or reduce aggressiveness in `eip1559Elasticity`.

**Tradeoff**

* **Pros:** Faster base fee response better captures demand; elasticity provides direct control over the gas target.
* **Cons:** Smaller denominator and/or aggressive elasticity increases per-block swings and increases fee volatility.

***

### Calldata-heavy transactions

**What you'll see**

* L1 data fee becomes a larger share of total cost for calldata heavy transactions (the L1 fee scales with compressed calldata size).
* Increasing `basefeeScalar` increases the per-byte L1 charge, making calldata heavy transactions more expensive.

**What to tweak**

* `basefeeScalar` and `blobBaseFeeScalar`:
  * Increase them if you need to recover more L1/DA posting costs from data heavy transactions.
  * Decrease them if you want to reduce user cost for calldata/blob-heavy workloads.

**Tradeoff**

* **Pros:** Enables proportional recovery of L1/DA posting costs.
* **Cons:** Penalizes calldata/blob-heavy dapps/users. Aggressive values can impact UX and reduce activity.

***

### Predictable operator revenue

**What you'll see**

* Introducing or increasing `operatorFeeScalar` raises the per-gas operator charge and increases predictable revenue per transaction.
* `operatorFeeConstant` adds a flat per-transaction fee regardless of gas usage.

**What to tweak**

* `operatorFeeScalar` and `operatorFeeConstant`:
  * Use when you want direct, predictable operator revenue independent of congestion and L1 fee dynamics.

**Tradeoff**

* **Pros:** Direct and predictable revenue per transaction.
* **Cons:** May discourage low-value transactions and changes transaction economics; should be used carefully. Any non-zero operator fee makes the chain configuration non-standard.

***

### DA-heavy workloads / DA-spam resistance

**What you'll see**

* DA footprint can limit how much transaction data fits into a block through scaled accounting of compressed DA usage.
* Increasing `daFootprintGasScalar` raises the gas charged per DA-byte footprint, reducing DA capacity for the same byte footprint and deterring DA-heavy patterns.

**What to tweak**

* `daFootprintGasScalar`:
  * Default is **400**, and `0` is treated as the default.
  * Setting it to **1** disables the DA footprint limiting behavior.

**Tradeoff**

* **Pros:** Deters DA spam and makes DA costs explicit in block accounting.
* **Cons:** Increasing it reduces DA capacity and may throttle the batcher or exclude legitimate DA-heavy workloads if set too aggressively.

***

## Summary

1. Make sure to check your current hardfork, this doc applies to Jovian and following hardforks.
2. Check the current fee parameters on your SystemConfig contract (see the [fee parameters reference](/chain-operators/reference/fee-parameters) for the expected values on OP Mainnet).
3. Make small changes and observe: vault balances, inclusion times, dropped txs, DA throttling, etc.
4. Extensively test all changes on a staging/testnet.
5. Communicate changes to dapp/wallet teams (gas estimation will change).

***

## References

* [Fee parameters reference](/chain-operators/reference/fee-parameters)
* [Transaction fees on OP Mainnet](https://docs.optimism.io/op-stack/transactions/fees#transaction-fees-on-op-mainnet)
* [Operator fee](https://docs.optimism.io/op-stack/transactions/fees#operator-fee)
* [L1 data fee](https://docs.optimism.io/op-stack/transactions/fees#l1-data-fee)
* [SystemConfig interface](https://github.com/ethereum-optimism/optimism/blob/develop/packages/contracts-bedrock/interfaces/L1/ISystemConfig.sol)
* [DA footprint](https://docs.optimism.io/notices/archive/upgrade-17#block-header-changes)
* [EIP-1559](https://docs.optimism.io/op-stack/protocol/differences#eip-1559-parameters)
* [OP Mainnet values](https://etherscan.io/address/0x229047fed2591dbec1eF1118d64F7aF3dB9EB290#readProxyContract)