Plain-language explanation of Mantle L1 data availability cost versus L2 execution cost.

How Mantle gas works

Mantle transaction cost has two major pieces:

1. L2 execution cost — the EVM work performed on Mantle: storage reads/writes, calls, logs, arithmetic, memory expansion, and contract creation.
2. L1 data availability cost — the cost of publishing transaction data so it can be reconstructed and verified outside the L2 execution environment.

A gas optimization can improve one piece and leave the other unchanged. A good Mantle report explains which part changed.

L2 execution cost

This is the familiar EVM gas dimension. Examples:

• replacing repeated storage reads with a cached local variable,
• using calldata instead of copying arrays into memory,
• packing storage variables,
• replacing revert strings with custom errors,
• avoiding unnecessary external calls.

These changes reduce the gas used by contract execution.

L1 data availability cost

Data availability cost is tied to the bytes a transaction contributes to the data posted for verification. On Mantle, receipt-level l1Fee is the production truth Archon uses when it is available.

Examples that affect DA cost:

• smaller calldata,
• fewer or smaller emitted log topics/data,
• compact batch operations,
• avoiding unnecessary large byte arrays,
• changing an interface from verbose dynamic data to compact fixed-size values.

Worked example

Imagine a claim function accepts a dynamic proof and emits a verbose event:

function claim(uint256 amount, bytes calldata proof) external {
    _verify(proof, msg.sender, amount);
    claimed[msg.sender] = true;
    emit Claimed(msg.sender, amount, proof);
}

A patch changes the event to log only the proof hash:

function claim(uint256 amount, bytes calldata proof) external {
    _verify(proof, msg.sender, amount);
    claimed[msg.sender] = true;
    emit Claimed(msg.sender, amount, keccak256(proof));
}

What changed?

• Execution: the patched version adds a keccak256 over the proof, which may slightly increase L2 execution gas.
• Data availability: the event no longer includes the full proof bytes, so the transaction receipt/log data is smaller. If the proof is large, DA cost can drop materially.
• Product interpretation: this is a good Mantle optimization only if the proof itself is already available elsewhere or does not need to be reconstructed from the event.

A report that says only “gas down” is incomplete. Archon should state whether the saving came from execution, calldata/log bytes, or both.

How Archon treats DA evidence

Archon does not rely on the legacy GasPriceOracle.getL1Fee(bytes) wording that previously produced a large mismatch against observed Mantle receipt fees. When receipt l1Fee exists, Archon treats it as source-of-truth telemetry. When it is missing, estimates must be labeled as estimates.