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Web3J

Web3J is a Java and Android library that connects application code to Ethereum clients and provides tools for working with wallets, JSON-RPC and smart contracts.

Explore the practical guide ↓

Independent OpenViST project profile, based on linked sources.

Web3J — OpenViST project profile in Developer Tools.
OpenViST project illustration. See the linked sources for product details.
Understand the project

Practical overview

When it fits

Use Web3J when a Java or Android project needs a code-level connection to Ethereum clients or Java interfaces for smart contracts, rather than writing that integration layer itself.

Who it is for

  • Java developers building applications that communicate with Ethereum clients.
  • Android developers integrating Ethereum client functionality.
  • Developers generating Java wrappers for Solidity or Truffle smart-contract definitions.

Documented uses

  • Call Ethereum JSON-RPC APIs over HTTP or IPC from Java code.
  • Use Ethereum wallet functionality in an application.
  • Generate Java wrappers to create, deploy, transact with and call smart contracts.
  • Work with reactive filters or ENS from Java.
Before you choose

Requirements & limits

The repository is public and identifies Web3J as open source. Java dependency use requires Java 21 or newer; Android has a separately named dependency artifact.

  • Choose the Java artifact for Java projects and the separately documented Android artifact for Android.
  • The library supports HTTP and IPC, but Unix IPC is unavailable on Android.
  • Alchemy and Infura are listed as options for connecting without running an Ethereum client yourself.
  • Smart-contract wrapper generation supports Solidity and Truffle definition formats.

Check current requirements in the official documentation. Source-based guidance does not mean OpenViST has run or independently tested this project.

Source-based practical guide

Add Web3J to a Java or Android project

Declare the documented Web3J core dependency in a Maven or Gradle project.

Before you start

  • A Java project using Java 21 or newer, or an Android project.
  • Maven or Gradle.

Steps

  1. For Maven Java projects, declare org.web3j:core:6.0.0.

  2. For Gradle Java projects, add implementation ('org.web3j:core:6.0.0').

  3. For Android, use org.web3j:core:4.12.3-android in the corresponding Maven or Gradle dependency declaration.

Expected outcome

The project declares the Web3J core library, using the Java or Android artifact as appropriate.

Guide limitations

  • The Java binaries require Java 21 or newer.
  • Unix IPC is not available on Android.
Documentation 1 ↗
Evidence and transparency

Sources & review

Official repository ↗
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17 October 2026
Original website title
LFDT-web3j/web3j · Official homepage title · retained in its source language
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