npm buidler


This plugin integrates Web3.js 0.20x into Buidler.


This plugin brings to Buidler the Web3 module and an initialized instance of Web3.


npm install --save-dev @nomiclabs/buidler-web3-legacy [email protected]^0.20.7

And add the following statement to your buidler.config.js:



This plugin creates no additional tasks.

Environment extensions

This plugin adds the following elements to the BuidlerRuntimeEnvironment:

  • Web3: The Web3.js module.
  • web3: An instantiated Web3.js object connected to the selected network.
  • pweb3: A promisified version of web3.


In Web3 0.20x some features are synchronous and some are asynchronous. For example web3.eth.accounts and web3.eth.blockNumber are synchronous and not supported. You'll get a Synchronous requests are not supported, use pweb3 instead error when trying to access them. To use these you need to use the promisified web3 and call the getter version of the property instead: await pweb3.eth.getAccounts().

TypeScript support

You need to add this to your tsconfig.json's files array: "node_modules/@nomiclabs/buidler-web3-legacy/src/type-extensions.d.ts"