Massa web3

massa-web3 is a TypeScript library that allow you to interact with the Massa blockchain through a local or remote Massa node. In particular the massa-web3 library will allow you to call the JSON-RPC API, but also to fetch and poll events from smart contracts on the Massa blockchain, deploy smart contracts and much more. Documentation for the massa-web3 library is available on the Github repository. The library is published on npmjs under @massalabs/massa-web3

create-react-app-massa is a minimal React template made for our massa-web3 library.

You’ll find examples of frontends using the massa-web3 library in the massa-sc-examples repository:

  • blog is an example of a decentralized blog platform.

Building Decentralized Application

For the decentralized website part, we’ll assume that you have some familiarity with HTML and JavaScript. If you want to have more details, you can follow this great tutorial from React from which the dApp is inspired from.

Here you can find an example dApp for the sum smart-contract: Massa DApp example: Sum.

  • having Thyra installed and running on your computer

  • having a wallet in Thyra

  • the wallet needs to own some Massa coins

  • having a smart contract deployed

Network: as any blockchain is a network of nodes, there could be practically several networks of different nodes. The main Massa network is called the MainNet. There is also a TestNet which is ran by Massa Labs team, where you can build applications without paying real Massa coins. You can also run your own network, with only one node (see Local network generation).

A decentralized application is an application running on a blockchain. Even the frontend can be hosted on the blockchain with web-on-chain.

To build such application you will need to use some libraries:

Then you will be able to build a frontend application that communicates with Thyra’s API to sign transactions and submit it to the blockchain.

Then, use Thyra to deploy your frontend application.


This section will give you some tips on how to debug your dapp while building it.

Work in a local development environment

Run a local node.

Start Thyra and bind it to your local node:

go run ./cmd/thyra-server/main.go --node-server LOCALHOST

Create a new wallet in Thyra.

Modify the file massa-node/base_config/initial_ledger.json:

    "ADDR": {
        "balance": "80000000",
        "datastore": {},
        "bytecode": []

to add some Massa tokens to your newly created address.

In your smart-contract projects, use this .env file:


Use the secret key that the node-client gave you when calling wallet_generate_secret_key. This wallet also needs to have some Massa coins, so it must appear in massa-node/base_config/initial_ledger.json before running the node with cd massa-node && cargo run –features sandbox in massa directory.

Modify the file massa/massa-client/base_config/config.toml to the localhost RPC:

ip = ""
private_port = 33034
public_port = 33035

Start a client with the command cargo run in massa/massa-client directory.

You might want to sign transactions to call smart contracts in your frontend application:

const options = {
  method: "POST",
  url: "https://my.massa/cmd/executeFunction",
  headers: { "Content-Type": "application/json" },
  data: {
    nickname: "wallet",
    name: "hello",
    at: "A1nyzu9rJKnf2zz8F7mkM5d6ZoThnMuAtUdij9WmcwXWMWJFmEB",
    args: "",
    gaz: { price: 1000, limit: 700000000 },
    coins: 0,
    expiry: 3,
    fee: 0,
    keyId: "default",

return axios
  .then(function (response) {
  .catch(function (error) {

This performs an HTTP POST call to Thyra, asking to create a transaction that will call the function named hello of the smart contract located at A1nyzu9rJKnf2zz8F7mkM5d6ZoThnMuAtUdij9WmcwXWMWJFmEB with the wallet name wallet.

This opens a password prompt and you will be able to see the response of the call in the development tools of the browser. The response is the operation id, for example 2mLLkdKB4BY4hJQFNwGZ5oQVhky13EVZAwHJXCGQnd3FRHUoHw.

If the operation failed, the response will contain the details.

Now you can now use commands of the node client to see the details of your operation:

get_operations 2mLLkdKB4BY4hJQFNwGZ5oQVhky13EVZAwHJXCGQnd3FRHUoHw

This will output something like

Operation 2oCTeeYMUt6hQuGAzCWbGBajXPPhz48VfHaEMWd6MJkVywa7Sa[ (in pool)]
In blocks:
  - 2Fvqyzd7jfYjPxS9t9UCEGoHhhuvD8HHAmD45CNzEnFp4bbFT5
Signature: ELrvQeuso9pjk5ErcG4WjESDpV8iFdweB45jic2UErSugSLLinbqx6JeKamxfXRZtBQoZi9ZcbvsGK858yx2FPsUoHrJJ
Creator pubkey: P12fnkn6fMhjZHatWsQ3k1L4B7hb99XdjbWCmVthxCwbisRAMk2P
Creator address: A12LempfubRfRZoRh7Dr4nWyTUYKAQs7Be1cZ9Gejcx7NXYG4HXD
Id: 2oCTeeYMUt6hQuGAzCWbGBajXPPhz48VfHaEMWd6MJkVywa7Sa
Fee: 0
Expire period: 2314
Operation type: CallSC:
  - target address:A1nyzu9rJKnf2zz8F7mkM5d6ZoThnMuAtUdij9WmcwXWMWJFmEB
  - target function:sum
  - target parameter:
  - max_gas:700000000
  - coins:0


target parameter is empty because parameters are encoded into bytes so it is unlikely to have printable characters.

You can also see events emitted by your contract (assuming that your contract is deployed at A1nyzu9rJKnf2zz8F7mkM5d6ZoThnMuAtUdij9WmcwXWMWJFmEB):

get_filtered_sc_output_event caller_address=A1nyzu9rJKnf2zz8F7mkM5d6ZoThnMuAtUdij9WmcwXWMWJFmEB
Context: Slot: (period: 2238, thread: 22) at index: 0
On chain execution
Origin operation id: 24kaBAdcCHUsgcfCUBxUXNBquJyz91Whon1xwbWmux1j29MEC
Call stack: A12LempfubRfRZoRh7Dr4nWyTUYKAQs7Be1cZ9Gejcx7NXYG4HXD,A1nyzu9rJKnf2zz8F7mkM5d6ZoThnMuAtUdij9WmcwXWMWJFmEB

Data: Sum (2, 3) = 5

In this example the event message is Sum (2, 3) = 5.