Gas Optimization with Hardhat Analyzer

Every operation on the EVM consumes gas, measured in units. Gas ensures resource usage is accounted for and prevents abusive loops. Gas fees follow the formula:

Higher gas usage increases transaction costs for users. Thus, reducing gasUsed is a top priority for dApp developers.

Hardhat Analyzer is a plugin that hooks into Hardhats compilation and testing tasks to produce detailed gas usage reports. Features include:

• Per-function and per-modifier gas consumption
• Comparison between different contract revisions
• Integration with Hardhat tasks: npx hardhat analyze
• HTML and JSON output for CI integration

For more, visit the official Hardhat Analyzer page: hardhat-analyzer.

1. Ensure you have Hardhat installed: npm install --save-dev hardhat.
2. Install the Analyzer plugin:
   npm install –save-dev @nomicfoundation/hardhat-analyzer
3. Update hardhat.config.js:
   require(@nomicfoundation/hardhat-analyzer)
   module.exports = {
   nbspnbspsolidity: 0.8.19,
   nbspnbspanalyzer: {
   nbspnbspnbspnbspenabled: true,
   nbspnbspnbspnbspoutputPath: gas-reports,
   nbspnbsp}
   }

Run the analyzer alongside tests:

The plugin generates an HTML report listing each function’s gas consumption:

Use the report to identify gas-heavy functions for targeted optimization.

• Packing Storage Variables
  • Group uint256 and smaller types to fit into single 32-byte slots.
  • Example: uint128 a uint128 b instead of two uint256.
• Short-Circuiting and Modifiers
  • Use require checks early to save gas on failed calls.
  • Implement modifiers for common validation logic.
• Use of immutable and constant
  • Declare fixed addresses or values as constant or immutable.
• Library Functions
  • Move reusable logic to library contracts (deployed once).
• Unchecked Math
  • Use unchecked { ... } blocks when overflow checks are not needed (Solidity ≥0.8).
• Event Parameter Optimization
  • Use indexed params selectively to minimize topics cost.
• Avoid Complex Data Structures
  • Prefer simple mappings or arrays over nested structs for hot paths.

A token transfer function was consuming ~65,000 gas. After optimizations:

The savings came from variable packing, unchecked math, and pre‐computed constants.

Integrate gas analysis into CI pipelines to track regressions:

• Run npx hardhat analyze --json in your CI workflow.
• Compare JSON outputs against a baseline commit.
• Fail builds on significant gas spikes.

• Test Thoroughly: Gas optimizations can introduce subtle bugs—cover every code path.
• Maintain Readability: Don’t over‐optimize at the cost of clarity.
• Benchmark on Testnet: Verify gas measurements on networks like Goerli.
• Monitor Upgrades: Every Solidity version brings new optimizer improvements keep dependencies updated.