L2 Gas Savings Calculator

WHAT IT DOES

L2 Gas Savings Calculator is a powerful cost-optimization tool that calculates potential gas savings by executing transactions on Layer 2 networks instead of Ethereum mainnet. When you're about to execute any transaction on Ethereum mainnet, the tool automatically fetches current gas prices from Ethereum and multiple L2 chains (Arbitrum, Optimism, Base, zkSync) via eth_call to RPC endpoints, estimates the total transaction cost in ETH and USD for each chain, and displays a side-by-side comparison. The panel shows the mainnet cost, each L2's cost, and the percentage and absolute savings for each L2—typically 70-90% savings on gas fees. Bridge cost estimates are included (when enabled) to provide a realistic total cost including the cost of moving funds to the L2. The tool highlights the best L2 option with a star and provides a "Switch to L2" button that opens the recommended L2's bridge interface. Gas savings history is tracked, providing visual feedback on cumulative savings over time.

WHERE IT RUNS

This overlay operates on any website (matching all URLs) across the entire web. It works in any browser that supports the BotGentz extension framework and has an EVM-compatible wallet extension installed. The panel activates automatically on every page, monitoring for transaction activity and providing L2 cost comparisons.

HOW TO USE

Install the extension and connect your wallet. When you're on Ethereum mainnet and about to execute a transaction, the panel automatically calculates L2 gas savings and displays the comparison. Review the cost comparison showing mainnet cost versus each L2 cost, with savings percentages and absolute savings in USD. If an L2 offers significant savings (configurable threshold), the panel highlights it as recommended. Click the "Switch to [L2]" button to open the L2 bridge interface and move funds for execution. Configure settings including preferred L2s to compare, savings threshold for highlighting (default 20%), bridge cost inclusion toggle, display currency (ETH or USD), and auto-suggest L2 toggle. Use the "Refresh" button to manually update gas prices and "Copy Report" to export a summary. The tool also tracks and displays your savings history.

MECHANISM: MULTI-CHAIN GAS PRICE FETCHING WITH BRIDGE COST INTEGRATION

The extension implements a parallel gas price fetching system that queries Ethereum mainnet and multiple L2 networks simultaneously. For each supported network, the tool uses eth_gasPrice via public RPC endpoints to fetch the current gas price in Gwei, then calculates the total transaction cost using a configurable gas limit estimate (default 100,000 gas units). The cost is displayed both in the network's native token and in USD using token price data from a price oracle. The bridge cost estimation uses heuristic fee structures typical of major L2 bridges (Across, Hop, etc.), calculating both the base fee and a variable percentage of the bridge amount. The net savings calculation subtracts the bridge cost from the L2 savings, providing a realistic total cost comparison for users who don't already have funds on the L2. The recommendation engine identifies the L2 with the highest net savings (savings minus bridge cost) and highlights it with a star icon. All gas price data is cached with a TTL to minimize RPC calls, and the tool automatically updates at configurable intervals. Savings history is stored locally using GM_setValue, tracking each L2 comparison with the percentage savings and USD amount, providing a running total of estimated savings over time. The tool also detects the current network via eth_chainId and automatically adjusts the comparison to only show relevant L2s for the current chain context.

THE PANEL

The overlay panel is fully draggable via its title bar and remembers its position per-site using GM_setValue. It snaps to the nearest edge when dragged within 40px of any screen boundary. The panel includes clear sections for L2 gas savings (domain, wallet address, network indicator), mainnet cost (gas price, total cost in ETH and USD), L2 comparison (list of L2s with gas price, cost, savings percentage, savings USD, bridge cost, and net savings), suggestion (recommended L2 with savings summary and Switch button), savings history (recent comparisons with percentage and USD savings), settings (L2 selection dropdown with Add button, savings threshold input, bridge cost toggle, auto-suggest toggle, notification toggle), and action buttons (Refresh, Save Settings, Copy Report, Clear History). The L2 comparison section color-codes savings—green for high, yellow for moderate, red for negative—making it easy to identify the best option. Pressing Escape temporarily dismisses the panel until you navigate to a new page or manually reactivate.

PLEASE NOTE

This extension requires the free BotGentz framework extension to be installed and active. You must also have a real EVM-compatible wallet extension (such as MetaMask, WalletConnect, Coinbase Wallet, or Rabby) already installed in your browser—the overlay uses your wallet's RPC provider for eth_gasPrice and eth_chainId calls. This tool is read-only—it does not send transactions or bridge funds; it only provides cost comparisons and bridge suggestions. The tool cannot estimate gas costs for transactions involving custom logic or complex contract interactions without accurate gas estimation; depends on RPC endpoints that may be rate-limited or unavailable; cannot predict gas price fluctuations that occur between comparison and transaction execution; bridge cost estimates are approximate and may not reflect actual bridge fees; cannot guarantee that the recommended L2 is compatible with the specific dApp or transaction type; does not support non-EVM chains where gas mechanics differ; cannot account for L2-specific fees (e.g., compression fees) that may not be captured in standard gas estimation; and does not support all L2 networks or all bridge protocols. No private keys, wallet balances, browsing history, or transaction data are ever collected, transmitted, or stored outside your local browser—all data is stored locally using GM_setValue. L2 gas savings are estimates only—always verify the actual transaction cost in your wallet before confirming. Moving funds to L2s requires separate bridge transactions with their own costs and risks.