Welcome to the first part of our comprehensive Kotlin Multiplatform for absolute beginners journey! If you’re reading this, chances are you’re tired of writing the same business logic twice: once for Android and once for iOS. Well, you’re in the right place. By the end of this series, you’ll have built a complete cross-platform app that shares code between Android and iOS while still delivering native performance and a smooth user experience.

What is Kotlin Multiplatform, Really?

Before we dive into the technical setup, let’s clear up what Kotlin Multiplatform actually is – because there’s a lot of confusion out there.

Kotlin Multiplatform is not a cross-platform UI framework like Flutter or React Native. Instead, it’s a technology that allows you to share your business logic, data models, and networking code between different platforms while keeping the UI completely native.

Think of it this way: imagine you’re building a recipe app. With KMP, you can share:

• The recipe data models
• The logic for fetching recipes from an API
• The algorithm for calculating nutritional information
• The database operations for saving favorite recipes

But the actual screens, buttons, and navigation? Those remain completely native – SwiftUI for iOS and Jetpack Compose (or Views) for Android.

Why Should You Care About Kotlin Multiplatform?

Let me share a story. Last year, I worked with a startup that was building a fitness tracking app. They had separate teams for Android and iOS, and every time they wanted to add a new feature – like a new workout calculation or a different way to sync data – they had to implement it twice. Not only did this take twice as long, but bugs would appear on one platform and not the other. Sound familiar?

Here’s what KMP solves:

1. Reduced Development Time: Write your core business logic once, use it everywhere.

2. Fewer Bugs: When your calculation logic is shared, you can’t have different bugs on different platforms.

3. Easier Maintenance: Update your business rules in one place instead of two (or more).

4. Native Performance: Unlike some cross-platform solutions, KMP compiles to native code, so there’s no performance penalty.

5. Gradual Adoption: You don’t have to rewrite your entire app. You can start by sharing just one feature.

What We’ll Build Together

Throughout this series, we’re going to build a simple but complete “Movie Database” app. It will:

• Fetch movie data from a real API
• Store favorite movies locally
• Display beautiful, platform-appropriate UI
• Handle offline scenarios
• Include proper error handling and loading states

By the end, you’ll have two native apps that share most of their logic but feel completely at home on their respective platforms.

Prerequisites: What You Need to Know

Don’t worry – you don’t need to be a Kotlin expert to follow along. Here’s what will help:

Required:

• Basic understanding of Android development (Activities, ViewModels)
• Some experience with Kotlin (if you’ve built a few Android apps, you’re good)
• Willingness to learn!

Nice to Have:

• Basic iOS development knowledge (we’ll explain the iOS parts)
• Familiarity with REST APIs
• Understanding of MVVM architecture

If you’re missing some of these, don’t panic. I’ll explain everything as we go, and I’ll provide resources for deeper learning.

Setting Up Your Development Environment

Alright, let’s get our hands dirty. Setting up KMP can be a bit tricky the first time, but I’ll walk you through every step.

Step 1: Install Android Studio

First, you’ll need Android Studio. Even if you’re primarily an iOS developer, Android Studio is currently the best IDE for Kotlin Multiplatform development.

1. Download Android Studio from developer.android.com
2. Install it with the default settings
3. Make sure you have the latest stable version (at least Android Studio Hedgehog)

Step 2: Install Xcode (Mac Only)

If you’re on Mac and want to build for iOS:

1. Install Xcode from the Mac App Store
2. Open Xcode and accept the license agreements
3. Install additional components when prompted

Windows/Linux Users: You can still follow along! You’ll be able to build and run the Android version and learn all the Kotlin Multiplatform concepts. The shared code we write will work on iOS too – you just won’t be able to run it locally.

Step 3: Install the Kotlin Multiplatform Plugin

1. Open Android Studio
2. Go to File → Settings (or Android Studio → Preferences on Mac)
3. Navigate to Plugins
4. Search for “Kotlin Multiplatform”
5. Install the plugin and restart Android Studio

Step 4: Verify Your Setup

Let’s make sure everything is working:

1. Open Terminal (or Command Prompt)
2. Run: ./gradlew --version (you should see Gradle version info)
3. For Mac users, run: xcode-select --version (should show Xcode command line tools)

Understanding the KMP Project Structure

Before we create our first project (that’s coming in Part 2!), let’s understand how a KMP project is organized. This will save you confusion later.

A typical Kotlin Multiplatform project looks like this:

MyApp/
├── shared/                   # This is where the magic happens
│   ├── src/
│   │   ├── commonMain/       # Code that runs on ALL platforms
│   │   ├── androidMain/      # Android-specific implementations
│   │   ├── iosMain/          # iOS-specific implementations
│   │   └── commonTest/       # Tests that run on all platforms
│   └── build.gradle.kts
├── androidApp/               # Your Android app
│   ├── src/main/java/
│   └── build.gradle.kts
├── iosApp/                   # Your iOS app
│   ├── iosApp.xcodeproj
│   └── iosApp/
└── build.gradle.kts

Here’s what each folder does:

shared/commonMain/: This is where you’ll spend most of your time. Any code you put here can be used by both Android and iOS. This includes:

• Data models (your Movie, User, etc. classes)
• Business logic (calculations, validations)
• API interfaces
• Database operations

shared/androidMain/ and shared/iosMain/: Sometimes you need platform-specific implementations. For example, showing a native date picker or accessing device-specific features. You define the interface in commonMain and provide platform-specific implementations here.

androidApp/: This is your regular Android app. It depends on the shared module and implements the UI using Activities, Fragments, Compose, etc.

iosApp/: This is your iOS app written in Swift/SwiftUI. It also uses the shared module but presents iOS-native UI.

Common Setup Pitfalls (And How to Avoid Them)

Having helped dozens of developers get started with KMP, here are the most common issues I see:

Pitfall 1: Wrong Android Studio Version

Problem: Using an old version of Android Studio that doesn’t play well with KMP. Solution: Always use the latest stable version. The KMP tooling improves rapidly.

Pitfall 2: Mixing Up Target Names

Problem: Getting confused between iosX64, iosArm64, and iosSimulatorArm64. Solution: Don’t worry about these details yet. The project templates handle this for you.

Pitfall 3: Expecting Flutter-Like UI Sharing

Problem: Thinking KMP will share your UI components. Solution: Remember, KMP shares business logic, not UI. UI stays native (which is actually a good thing!).

Pitfall 4: Overcomplicating the First Project

Problem: Trying to migrate an existing complex app to KMP right away. Solution: Start simple. Build a new small feature with KMP first.

What’s Coming Next?

In Part 2, we’ll create our very first Kotlin Multiplatform project from scratch. You’ll see:

• How to use the KMP project wizard
• Creating your first shared class
• Running the same code on both Android and iOS
• Understanding how the build system works

We’ll start with something super simple – a shared greeting function – and gradually build up to more complex features.

Key Takeaways

Before we wrap up, let’s recap the important points:

1. KMP shares business logic, not UI – your apps will still look and feel native
2. You can adopt it gradually – start with one small feature
3. Android Studio is your main IDE – even for the iOS parts
4. The setup can be tricky initially – but it gets easier
5. It’s about reducing duplicate logic – not about writing less code overall

Getting Help

As we go through this series, you might run into issues. Here are the best places to get help:

• Official Documentation: kotlinlang.org/docs/multiplatform.html
• KMP Community: Very active on Slack and Discord
• Stack Overflow: Tag your questions with kotlin-multiplatform
• This Series: I’ll be covering common issues as we encounter them

Ready for the Journey?

Setting up your development environment is the hardest part of learning KMP – and you’ve just completed it! In the next part, we’ll create our first project and write our first shared code. You’ll be amazed at how satisfying it is to see the same Kotlin code running on both platforms.

Take a moment to make sure your setup is working properly, and I’ll see you in Part 2 where the real fun begins!

Coming up in Part 2: We’ll use the Kotlin Multiplatform wizard to create our Movie Database project, write our first shared data class, and see it working on both Android and iOS. It’s going to be exciting!

Have questions about the setup? Drop them in the comments below, and I’ll help you get sorted before we move on to building our first app!

Kotlin Multiplatform – Top 5 FAQs

The most common questions developers ask when getting started with Kotlin Multiplatform.

1. Is Kotlin Multiplatform the same as Flutter or React Native?

No, they’re fundamentally different approaches. Flutter and React Native share UI components across platforms, while KMP shares business logic but keeps UI completely native.

Think of it this way:

• Flutter/React Native: “Write once, run everywhere” (including UI)
• Kotlin Multiplatform: “Write business logic once, native UI everywhere”

This means your apps will look and feel 100% native on each platform, but you won’t have to write your data models, API calls, and business calculations twice.

2. Do I need to know iOS development to use KMP?

Not initially! You can start by just building the Android side and sharing logic. However, to build the iOS app, you’ll eventually need basic Swift/SwiftUI knowledge.

The good news is that most of your complex logic will already be written in the shared module, so you’ll mainly be focusing on UI and navigation on the iOS side.

3. Can I use KMP in an existing project?

Absolutely! This is one of KMP’s biggest advantages. You don’t need to rewrite your entire app.

Start small:

• Extract one simple feature (like user data models) into a shared module
• Move API response parsing to shared code
• Share authentication logic between platforms
• Gradually expand from there

Many teams start by sharing just their data models and expand over time.

4. Do I need a Mac to develop KMP apps?

For Android development: No For iOS development: Yes

You can develop and test all your shared business logic on Windows, Mac, or Linux. But to compile and test iOS apps, you’ll need a Mac with Xcode.

However, since most of your logic will be in the shared module, you can develop and test the majority of your app’s functionality on any platform!

5. What about performance compared to native apps?

Excellent! KMP compiles to native code on each platform:

• Android: Compiles to bytecode (same as regular Android apps)
• iOS: Compiles to native ARM code
• No performance penalty compared to writing separate native apps

Companies like Netflix and Cash App use KMP in production with millions of users, proving it can handle enterprise-scale performance requirements.