Configuration

Your configuration file is called truffle-config.js and is located at the root of your project directory. This file is a Javascript file and can execute any code necessary to create your configuration. It must export an object representing your project configuration like the example below.

module.exports = {
  networks: {
    development: {
      host: "127.0.0.1",
      port: 8545,
      network_id: "*" // Match any network id
    }
  }
};

The default configuration ships with configuration for a single development network, running on 127.0.0.1:8545. There are many other configuration options, detailed below.

Note: This only applies to Truffle version 4 and below.

When using the Command Prompt on Windows, the default configuration file name can cause a conflict with the truffle executable, and so you may not be able to run Truffle commands properly on existing projects.

This is because of the way that command precedence works on the Command Prompt. The truffle.cmd executable is on the path as part of the npm package, but the truffle.js configuration file is in the actual directory where the truffle command is run. Because .js is an acceptable executable extension by default, truffle.js takes precedence over truffle.cmd, causing unexpected results.

Any of the following solutions will remedy this issue:

  • Call the executable file explicitly using its .cmd extension (truffle.cmd compile)
  • Edit the system PATHEXT environment variable and remove .JS; from the list of executable extensions
  • Rename truffle.js to something else (truffle-config.js)
  • Use Windows PowerShell or Git BASH, as these shells do not have this conflict.

Build configuration of your application, if your application requires tight integration with Truffle. Most users likely will not need to configure this option. See the Build Processes section for more details.

Specifies which networks are available for deployment during migrations, as well as specific transaction parameters when interacting with each network (such as gas price, from address, etc.). When compiling and running migrations on a specific network, contract artifacts will be saved and recorded for later use. When your contract abstractions detect that your Ethereum client is connected to a specific network, they'll use the contract artifacts associated that network to simplify app deployment. Networks are identified through Ethereum's net_version RPC call, as well as blockchain URIs.

The networks object, shown below, is keyed by a network name and contains a corresponding object that defines the parameters of the network. The networks option is required, as if you have no network configuration, Truffle will not be able to deploy your contracts. The default network configuration provided by truffle init gives you a development network that matches any network it connects to -- this is useful during development, but not suitable for production deployments. To configure Truffle to connect to other networks, simply add more named networks and specify the corresponding network id.

The network name is used for user interface purposes, such as when running your migrations on a specific network:

$ truffle migrate --network live

Example:

networks: {
  development: {
    host: "127.0.0.1",
    port: 8545,
    network_id: "*", // match any network
    websockets: true
  },
  live: {
    host: "178.25.19.88", // Random IP for example purposes (do not use)
    port: 80,
    network_id: 1,        // Ethereum public network
    // optional config values:
    // gas
    // gasPrice
    // from - default address to use for any transaction Truffle makes during migrations
    // provider - web3 provider instance Truffle should use to talk to the Ethereum network.
    //          - function that returns a web3 provider instance (see below.)
    //          - if specified, host and port are ignored.
    // skipDryRun: - true if you don't want to test run the migration locally before the actual migration (default is false)
    // timeoutBlocks: - if a transaction is not mined, keep waiting for this number of blocks (default is 50)
  }
}

For each network, if unspecified, transaction options will default to the following values:

  • gas: Gas limit used for deploys. Default is 6721975.
  • gasPrice: Gas price used for deploys. Default is 100000000000 (100 Shannon).
  • from: From address used during migrations. Defaults to the first available account provided by your Ethereum client.
  • provider: Default web3 provider using host and port options: new Web3.providers.HttpProvider("http://<host>:<port>")
  • websockets: You will need this enabled to use the confirmations listener or to hear Events using .on or .once. Default is false.

For each network, you can specify either host / port or provider, but not both. If you need an HTTP provider, we recommend using host and port, while if you need a custom provider such as HDWalletProvider, you must use provider.

The following network list consists of a local test network and an Infura-hosted Ropsten network, both provided by HDWalletProvider. Make sure you wrap truffle-hdwallet providers in a function closure as shown below to ensure that only one network is ever connected at a time.

networks: {
  ropsten: {
    provider: function() {
      return new HDWalletProvider(mnemonic, "https://ropsten.infura.io/v3/YOUR-PROJECT-ID");
    },
    network_id: '3',
  },
  test: {
    provider: function() {
      return new HDWalletProvider(mnemonic, "http://127.0.0.1:8545/");
    },
    network_id: '*',
  },
}

If you specify host and port instead of provider, Truffle will create its own default HTTP provider using that host and port, and no minimal network connection will be opened, so there is no need to do the function wrapping workaround. That said, you wouldn't be able to use a custom provider in this case.

The default directory for uncompiled contracts is ./contracts relative to the project root. If you wish to keep your contracts in a different directory you may specify a contracts_directory property.

Example:

To have Truffle find contracts in ./allMyStuff/someStuff/theContractFolder (recursively) at compile time:

module.exports = {
  contracts_directory: "./allMyStuff/someStuff/theContractFolder",
  networks: {
    development: {
      host: "127.0.0.1",
      port: 8545,
      network_id: "*",
    }
  }
};

Note: In addition to specifying a relative path, you can also use globs/regular expressions to selectively compile contracts.

The default output directory for compiled contracts is ./build/contracts relative to the project root. This can be changed with the contracts_build_directory key.

Examples:

To place the built contract artifacts in ./output/contracts:

module.exports = {
  contracts_build_directory: "./output",
  networks: {
    development: {
      host: "127.0.0.1",
      port: 8545,
      network_id: "*",
    }
  }
};

The built contract artifacts do not need to be inside the project root:

module.exports = {
  contracts_build_directory: "../../../output",
  networks: {
    development: {
      host: "127.0.0.1",
      port: 8545,
      network_id: "*",
    }
  }
};

Absolute paths will also work. This is not recommended though, as an absolute path may not exist when compiled on another system. If you use absolute paths on Windows, make sure to use double backslashes for paths (example: C:\\Users\\Username\\output).

The default migrations directory is ./migrations relative to the project root. This can be changed with the migrations_directory key.

Example:

module.exports = {
  migrations_directory: "./allMyStuff/someStuff/theMigrationsFolder",
  networks: {
    development: {
      host: "127.0.0.1",
      port: 8545,
      network_id: "*",
    }
  }
};

Configuration options for the MochaJS testing framework. This configuration expects an object as detailed in Mocha's documentation.

Example:

mocha: {
  useColors: true
}

In the compilers object you can specify settings related to the compilers used by Truffle.

Solidity compiler settings. Supports optimizer settings for solc.

You may specify...

  • any solc-js version listed at solc-bin. Specify the one you want and Truffle will get it for you.
  • a natively compiled solc binary (you'll need to install this yourself, links to help below).
  • a dockerized solc from one of images published here.
  • a path to a locally available solc
  • a solc-js parser for faster docker and native compilations

Truffle config example:

module.exports = {
  compilers: {
    solc: {
      version: <string>, // A version or constraint - Ex. "^0.5.0"
                         // Can also be set to "native" to use a native solc
      docker: <boolean>, // Use a version obtained through docker
      parser: "solcjs",  // Leverages solc-js purely for speedy parsing
      settings: {
        optimizer: {
          enabled: <boolean>,
          runs: <number>   // Optimize for how many times you intend to run the code
        },
        evmVersion: <string> // Default: "petersburg"
      }
    }
  }
}

For more information, please see the Solidity documentation on Compiler Input and Output JSON Description.

For more advanced use cases with artifact creation you can use the external compilers configuration. You can use this feature by adding a compilers.external object to your Truffle config:

module.exports = {
  compilers: {
    external: {
      command: "./compile-contracts",
      targets: [{
        /* compilation output */
      }]
    }
  }
}

When you run truffle compile, Truffle will run the configured command and look for contract artifacts specified by targets.

This new configuration supports a couple of main use cases:

  • Your compilation command outputs Truffle JSON artifacts directly. If your compilation command generates artifacts directly, or generates output that contains all the information for an artifact, configure a target as follows:
module.exports = {
  compilers: {
    external: {
      command: "./compile-contracts",
      targets: [{
        path: "./path/to/artifacts/*.json"
      }]
    }
  }
}

Truffle will execute your script, then expand the glob (*) and find all .json files in the listed path and copy those over as artifacts in the build/contracts/ directory.

  • Your compilation command outputs individual parts of an artifact, and you want Truffle to generate the artifacts for you. The above use case might not be sufficient for all use cases. You can configure your target to run an arbitrary post-processing command:
module.exports = {
  compilers: {
    external: {
      command: "./compile-contracts",
      targets: [{
        path: "./path/to/preprocessed-artifacts/*.json",
        command: "./process-artifact"
      }]
    }
  }
}

This will run ./process-artifact for each matched .json file, piping the contents of that file as stdin. Your ./process-artifact command is then expected to output a complete Truffle artifact as stdout.

Want to provide the path as a filename instead? Add stdin: false to your target configuration.

  • You can also specify the individual properties of your contracts and have Truffle generate the artifacts itself.
module.exports = {
  compilers: {
    external: {
      command: "./compile-contracts",
      targets: [{
        properties: {
          contractName: "MyContract",
          /* other literal properties */
        },
        fileProperties: {
          abi: "./output/contract.abi",
          bytecode: "./output/contract.bytecode",
          /* other properties encoded in output files */
        }
      }]
    }
  }
}

Specify properties and/or fileProperties, and Truffle will look for those values when building the artifacts.

To override the working directory for all specified paths and running commands, use the workingDirectory option. For instance, the following will run ./proj/compile-contracts and read ./proj/output/contract.abi:

module.exports = {
  compilers: {
    external: {
      command: "./compile-contracts",
      workingDirectory: "./proj",
      targets: [{
        fileProperties: {
          abi: "./output/contract.abi",
          bytecode: "./output/contract.bytecode",
        }
      }]
    }
  }
}

Note: This feature is new and still in a barebones state. Please let us know how we can improve it!

Provides Truffle with a list of installed third-party extensions installed as NPM package dependencies.

Truffle plugin support is currently limited to plugins that define custom workflow commands. For more information, see Third-Party Plugin Commands.

This configuration applies to the optional ethpm.json file that exists alongside your truffle.js configuration file.

Name of the package you're publishing. Your package name must be unique to the EthPM registry.

Example:

package_name: "adder"

Version of this package, using the semver specification.

Example:

version: "0.0.3"

A text description of your package for human readers.

Example:

description: "Simple contract to add two numbers"

An array of authors. Can have any format, but we recommend the format below.

Example:

authors: [
  "Tim Coulter <[email protected]>"
]

An array of keywords that tag this package with helpful categories.

Example:

keywords: [
  "ethereum",
  "addition"
],

A list of EthPM packages your package depends on, using semver version ranges, like npm.

Example:

dependencies: {
  "owned": "^0.0.1",
  "erc20-token": "1.0.0"
}

License to use for this package. Strictly informative.

Example:

license: "MIT",