Who Should Read This Document

This doc is for developers, and it aims to show how they can join the Loom Testnet and deploy their smart contracts. If you are looking for information on how to run nodes or to become a validator, please checkout our Validator Guide.


Deploying to Loom PlasmaChain is no different from deploying to the Ethereum main net, or to Rinkeby. If you know how to do one, you also know how to do the other.

We at Loom are using Truffle to build, test, and deploy our smart contracts. To make our life easier, we developed something called a provider that lets Truffle deploy to Loom PlasmaChain just like it deploys to Ethereum.

Without delving too much into details, the provider works like a bridge that makes Web3.js calls compatible with Loom PlasmaChain.

This document shows how you can use Truffle and the Loom Truffle Provider to build a simple Web UI that interacts with Loom PlasmaChain.


Make sure the following requirements are met and then follow the steps in the next section:

Node >= 8
yarn or npm

Setting Things Up

First, let's clone the Truffle DAppChainExample repository. Open a terminal, cd into the directory where you store your projects, and run the following command:

git clone https://github.com/loomnetwork/truffle-dappchain-example

Next, cd into truffle-dappchain-example:

cd truffle-dappchain-example

and run:

yarn install

Run against Loom Testnet

Generate the Loom private key

The following command will download the loom binary and generate the private key for you:

yarn gen:extdev-key

The Loom private key will be saved into a file called extdev_private_key.

Deploy to extdev_plasma_us1

As an example, we will deploy and run our application against extdev_plasma_us1.

Run the following command:

yarn deploy:extdev

The above command will compile and then deploy our smart contract to extdev_plasma_us1


Run this command below to send transactions to the smart contract deployed to extdev_plasma_us1:

yarn test:extdev

If everything looks good, let's spin up a web server and interact with our smart contract.

Start the Web Interface

The web interface is built with React and Webpack. Open a new terminal and run the following command:

yarn serve:extdev

The web interface is available on http://localhost:8080.

Run Against Local Loom Chain

The following command will download the loom binary and generate a new private key:

yarn gen:loom-key

The Loom private key will be saved into a file called loom_private_key.

Spin up Loom Chain

In a new terminal, run:

yarn loom:init

and then:

yarn loom:run

Deploy the Smart Contract

To deploy, run the following command:

yarn deploy


You can test the smart contract using:

yarn test

Web interface

We're ready to start the web server. In a new terminal, type:

yarn serve

Useful information

  1. In order to correctly redeploy the contracts, there's a command yarn deploy:reset.

  2. Also, is possible to call truffle directly with yarn truffle.

  3. We're not versioning the build directory for this particular example, although is recommended to do so. The limitation can be removed by editing the .gitignore file.