#Compiling your contracts

To compile your contracts in your Hardhat project, use the built-in compile task:

$ npx hardhat compile
Compiling...
Compiled 1 contract successfully

The compiled artifacts will be saved in the artifacts/ directory by default, or whatever your configured artifacts path is. Look at the paths configuration section to learn how to change it. This directory will be created if it doesn't exist.

After the initial compilation, Hardhat will try to do the least amount of work possible the next time you compile. For example, if you didn't change any files since the last compilation, nothing will be compiled:

$ npx hardhat compile
Nothing to compile

If you only modified one file, only that file and others affected by it will be recompiled.

To force a compilation you can use the --force argument, or run npx hardhat clean to clear the cache and delete the artifacts.

# Configuring the compiler

If you need to customize the Solidity compiler options, then you can do so through the solidity field in your hardhat.config.js. The simplest way to use this field is via the shorthand for setting the compiler version, which we recommend always doing:

module.exports = {
  solidity: "0.8.9",
};

We recommend always setting a compiler version in order to avoid unexpected behavior or compiling errors as new releases of Solidity are published.

The expanded usage allows for more control of the compiler:

module.exports = {
  solidity: {
    version: "0.8.9",
    settings: {
      optimizer: {
        enabled: true,
        runs: 1000,
      },
    },
  },
};

settings has the same schema as the settings entry in the Input JSON that can be passed to the compiler. Some commonly used settings are:

• optimizer: an object with enabled and runs keys. Default value: { enabled: false, runs: 200 }.

• evmVersion: a string controlling the target evm version. For example: istanbul, berlin or london. Default value: managed by solc.

If any of your contracts have a version pragma that is not satisfied by the compiler version you configured, then Hardhat will throw an error.