Fetching Data with Arweave JS

Arweave JS is the official JavaScript/TypeScript SDK for interacting with the Arweave network.

This guide covers the basics of fetching data from known transaction IDs.

Installation

NPM

npm install --save arweave

Initialization

Basic Initialization

import Arweave from "arweave";

// Initialize with default settings (recommended for web)
const arweave = Arweave.init({});

// Or specify a custom gateway
const arweave = Arweave.init({
  host: "arweave.net",
  port: 443,
  protocol: "https",
});

Fetching Data

Get Transaction Data

The recommended way to fetch transaction data:

const txId = "sHqUBKFeS42-CMCvNqPR31yEP63qSJG3ImshfwzJJF8";

// Get data as base64url encoded string
arweave.transactions.getData(txId).then((data) => {
  console.log("Raw data:", data);
});

// Get data decoded to Uint8Array (for binary data)
arweave.transactions.getData(txId, { decode: true }).then((data) => {
  console.log("Decoded data:", data);
});

// Get data decoded as string
arweave.transactions
  .getData(txId, { decode: true, string: true })
  .then((data) => {
    console.log("String data:", data);
  });

Get Full Transaction

Fetch complete transaction information including metadata:

const txId = "sHqUBKFeS42-CMCvNqPR31yEP63qSJG3ImshfwzJJF8";

arweave.transactions.get(txId).then((transaction) => {
  console.log("Transaction ID:", transaction.id);
  console.log("Owner:", transaction.owner);
  console.log("Data size:", transaction.data_size);
  console.log("Tags:", transaction.tags);

  // Note: data field may not be included for large transactions
  if (transaction.data) {
    console.log("Data included:", transaction.data);
  }
});

Working with Tags

Decode Transaction Tags

Tags are base64url encoded by default. Use the built-in decoder:

const txId = "sHqUBKFeS42-CMCvNqPR31yEP63qSJG3ImshfwzJJF8";

arweave.transactions.get(txId).then((transaction) => {
  transaction.tags.forEach((tag) => {
    // Decode tag name and value
    const key = tag.get("name", { decode: true, string: true });
    const value = tag.get("value", { decode: true, string: true });
    console.log(`${key}: ${value}`);
  });
});

Working with Different Data Types

JSON Data

const txId = "sHqUBKFeS42-CMCvNqPR31yEP63qSJG3ImshfwzJJF8";

arweave.transactions
  .getData(txId, { decode: true, string: true })
  .then((data) => {
    try {
      const jsonData = JSON.parse(data);
      console.log("JSON data:", jsonData);
    } catch (e) {
      console.log("Data is not valid JSON:", data);
    }
  });

Binary Data

const txId = "sHqUBKFeS42-CMCvNqPR31yEP63qSJG3ImshfwzJJF8";

arweave.transactions.getData(txId, { decode: true }).then((data) => {
  console.log("Binary data size:", data.byteLength);
  // data is a Uint8Array
});

Best Practices

Use getData() instead of get() when you only need the data
Always handle potential errors when fetching data
Check transaction status before processing data for critical operations
Use appropriate decoding options based on your expected data type

Resources

Arweave JS GitHub Repositoryopen in new window
GraphQL Guide - For finding transactions

Documentation

# Fetching Data with Arweave JS

# Installation

# NPM

# Initialization

# Basic Initialization

# Fetching Data

# Get Transaction Data

# Get Full Transaction

# Working with Tags

# Decode Transaction Tags

# Working with Different Data Types

# JSON Data

# Binary Data

# Best Practices

# Resources