B4X tools explained: B4A, B4i, B4J and B4R for cross-platform apps in BASIC

B4X is a family of development tools from Anywhere Software, a company that has specialized in mobile development since 2005. The idea is simple: write your app once in a modern, easy-to-read BASIC language and build native apps for Android, iOS, desktop, servers and even microcontrollers, reusing most of your code. In this article we look at what each tool does, who it is for, and how it compares with other cross-platform options in 2026.

A note on the language

The original version of this post (2014) described B4X as using VB.NET. That was not accurate. B4X uses its own BASIC dialect, which will feel familiar to anyone who has used Visual Basic, but it is not VB.NET and does not run on .NET. Under the hood, B4A and B4J compile to Java bytecode, B4i produces native iOS code, and B4R targets Arduino-style boards.

The four B4X tools

B4A: Android

B4A builds native Android apps. It includes a visual designer, a debugger that can hot-swap code while the app runs on a device, and a large set of libraries for things like databases, HTTP, Firebase and AdMob. B4A has been free since 2020, which makes it an easy way to start Android development.

B4i: iOS

B4i builds native iOS apps using the same concepts and much of the same code as B4A. It is a paid product. Building for iOS still needs Apple's tools, so you either use a Mac or Anywhere Software's hosted builder service, which lets you develop on Windows.

B4J: desktop, server and web

B4J creates desktop applications (Windows, macOS, Linux), server applications and web back ends. It also runs on ARM boards such as the Raspberry Pi. B4J is free, including for commercial use.

B4R: Arduino and ESP

B4R targets microcontrollers like Arduino and ESP8266/ESP32 boards, so you can write firmware in the same language as your apps. It is also free.

Why developers choose B4X

• Fast learning curve: the BASIC syntax is readable, and the IDE hides much of the Android and iOS boilerplate.
• Code sharing: "B4XPages" and cross-platform libraries let you share most of the logic and UI between Android, iOS and desktop.
• Native output: apps are compiled to native code for each platform, with no web view in between.
• Active community: the B4X forum is large and the developers answer questions there directly.

Limitations to keep in mind

• The ecosystem is smaller than Kotlin, Flutter, React Native or .NET MAUI, so you will find fewer third-party libraries and tutorials outside the official forum.
• New platform features sometimes need a library wrapper before you can use them.
• Hiring developers who already know B4X is harder than for mainstream stacks.

How it compares

If you already know C#, .NET for Android and .NET MAUI are the natural choice, and they are the stack most of the newer articles on this blog cover. If you prefer a single modern UI toolkit, Flutter is popular. B4X remains a good fit for solo developers, hobbyists and small teams who want to ship simple native apps quickly with very little setup.

Getting started

1. Download the IDE you need from the official site: b4x.com.
2. For B4A, install a Java JDK and the Android SDK as described in the installation guide.
3. Start with a B4XPages template and run it on your phone.

Video overview

Read more: our .NET for Android articles.