Before we get to the SDK and API topics, check out this list of RPC providers which you can review and setup your dedicated JSON-RPC endpoints ahead of time, to be used by your app. The endpoints are either free-to-use or have a generous allowance*, where developers can focus on developing apps, rather than setting up a blockchain infrastructure.

QuickNode

Announcement

Features

• Full Archive Support.

• Automatic geo-routing for fastest response times.

• Support for QuickNode Marketplace add-ons.

• Free plans.

• Dedicated support on paid plans.

Instructions

• QuickNode Harmony RPC docs

Ankr

Announcement

Features

• Public RPC Endpoint: https://rpc.ankr.com/harmony

• Archive Support

• Automatic geo-routing across North America, Europe, Asia for fast requests

• Nodes aggregated from Ankr, Pocket, and Harmony for improved decentralization

• High Rate Limits

Instructions

• RPC support available on the Ankr Discord

Chainstack

Announcement

Instructions

Tutorials

Discussions

Pocket Networks

Announcement

Instructions

Discussions

GetBlock

Endpoint

Instructions

1RPC (Automata Network)

Announcement

Features

• Harmony 1RPC Endpoint: https://1rpc.io/one

• Free RPC relay to eradicate metadata exposure and leakage with a one-click experience for users within Web3

• A proxy layer that shields user data before it reaches existing RPC endpoints

Instructions

• 1RPC docs

• 1RPC support available on the Automata Network Discord

NOWNodes

Announcement

• Announcement

• Twitter

Endpoint

Harmony RPC Endpoint: https://nownodes.io/nodes/harmony-one

'https://one.nownodes.io/yourAPI-key'

Features

• Free plan is available.

• Dedicated plan with no rate limits is available by request.

Remix is a powerful, open source tool that helps you write Solidity contracts straight from the browser. Written in JavaScript, Remix supports both usage in the browser and locally.

Remix also supports testing, debugging and deploying of smart contracts and much more.

Ethereum remix can be directly used along with metamask using harmony custom rpcs as described in here.

However, we also have forked Remix and customized to Harmony here. A guide for deploying smart contracts using Harmony Remix is provided here.

Most of the blockchain apps are developed in JavaScript, hence setting up Node.js is the first step.

Install Node.js

Skip this section if Node.js >=12.0is already installed.

Ubuntu

sudo apt update
sudo apt install curl git
curl -sL https://deb.nodesource.com/setup_12.x | sudo -E bash -
sudo apt install nodejs

MacOS

curl -o- https://raw.githubusercontent.com/creationix/nvm/v0.35.2/install.sh | bash
nvm install 12
nvm use 12
nvm alias default 12
npm install npm --global # Upgrade npm to the latest version

Windows

Get node-v12.XX.XX-x64.msi from here

Harmony ONE is an Ethereum EVM 100% compatible blockchain, and is very good at decentralized application (Dapp) development within many possible verticals including DeFi, NFT, Gaming, and many others.

You can read more about Harmony One Ecosystem - here

Useful articles:

Harmony & Web3

Harmony & Metamask

Harmony & Ethereum Developer Ecosystem

Examples of Harmony projects that use Ethereum RPC

Network Status

https://status.harmony.one

Chainid

Block Explorers

Faucets

Overview

Harmony is a powerful blockchain that is EVM compatible with sharding and staking features. Developing on Harmony should feel very familiar for Ethereum developers, as Harmony is fully Ethereum compatible and inherits almost all the tools and libraries from Ethereum, like truffle, remix, web3js, etc.

The simplest way to interact with Harmony blockchain is via JSON RPCs.

Querying Harmony blockchain using JSON RPCs

• JSON RPCs and curl command examples

To really explore the full potential of Harmony blockchain, creating a wallet is the next step.

Creating a wallet (or ONE address)

• Using MetaMask or mathwallet browser extensions. Any other wallets can also be used.

• Harmony CLI, also provides a quick way to create/manage wallet, interact with blockchain, etc.

Development environments

• Several development environments exists: mainnet, testnnet, localnet

• Testnet faucet

  • https://faucet.pops.one

  • https://chaindrop.org

• Blockchain Explorers

  • Mainnet: https://explorer.harmony.one

  • Testnet: https://explorer.testnet.harmony.one

We provide SDKs in several different languages. However most feature complete is our JavaScript SDK, which is the preferred language for DApp development.

Using SDKs to interact with Harmony blockchain

• About SDKs

• The most popular is our JavaScript SDK, which includes examples, documentation, and DApps developed in previous hackathons

• Other SDKs include: Golang CLI, Java SDK, Python SDK

  • Note that, the Python SDK has only read-only features, meaning no transaction signing or smart contracts

How to deploy a smart contract on Harmony?

• Tutorial

• Github repo

• Interacting with wallets programmatically

How to create a simple DApp on Harmony?

One of the best ways to get started is to use scaffold-eth which now has integrated Harmony support.

You can also use the Harmony DApp template generator to get started.

• Tutorial

• GitHub repo

Many other examples and DApps can be found in the SDK repo and under showcases.

Resources

• talk.harmony.one - for reporting issues, asking questions, or interact with other developers

• Harmony GitHub

• Harmony dev Reddit

• Discord channels: #developers, #development

• Harmony dev Telegram

Known Limitations

• Only cross-shard native token (ONE token) transfers are allowed. No cross-shard for HRC20 or other contracts. Meaning, smart contracts are deployed on shard-0 and all contract interactions happen on shard-0. Contracts can still be deployed on other shards, however they won't be able to interact with contracts in other shards. We have cross-shard smart contract on our roadmap for 2023.