Introduction to Kotlin Multiplatform (KMP)
Welcome to the very first class of our Kotlin Multiplatform (KMP) tutorial series!
Today is special — not because we’re learning a new technology, but because you’re stepping into a new way of thinking about app development.
For years, developers building for Android, iOS, Web, and Desktop faced one classic problem:
“Why am I writing the same logic again and again in different languages?”
Kotlin Multiplatform finally answers that.
Why KMP is Amazing for Beginners
- No need to learn Swift or SwiftUI to make iOS apps
- No need to learn JavaScript for web
- Write once → run everywhere
- Compose multiplatform for beautiful UI
1. What Exactly Is Kotlin Multiplatform?
Think of KMP as a superpower built inside Kotlin.
It lets you write certain parts of your app once and use them everywhere:
- Android
- iOS
- Web (JavaScript)
- Desktop (Windows, macOS, Linux)
But here’s the best part:
KMP doesn’t force you to rewrite your UI.
You keep the native UI frameworks you love:
- Android → Jetpack Compose
- iOS → SwiftUI / UIKit
KMP shares only what makes sense to share:
- Business logic
- Networking
- Database
- Models
- Utility classes
- Authentication logic
- Algorithms
- Data formatting
- API code
This gives you freedom + speed at the same time.
2. Why is KMP Becoming Popular?
Let’s break it down:
🧩 a) Less Repetition, More Creativity
No more copying the same API code 4 times.
You write once → run everywhere.
🚀 b) Faster Development
Shared logic = consistent behaviour across platforms + less debugging.
💸 c) Saves Money & Team Effort
Your Android & iOS teams can finally collaborate instead of building the same thing separately.
🔧 d) Mature Ecosystem
Kotlin team is improving KMP rapidly.
Libraries you use daily now support KMP:
🏆 e) Backed by JetBrains + Google
Kotlin is the official Android language.
Now it evolves into a cross-platform ecosystem.
3. How Does KMP Work Behind the Scenes?
Imagine KMP as a house with three floors:
1️⃣
Common code (shared)
Written in pure Kotlin.
Contains business logic: API calls, validation, caching, etc.
2️⃣
Platform-specific code
Only when needed.
For example:
- Accessing Android permissions
- Using iOS camera
- Reading local storage on Desktop
KMP provides a system called expect/actual for this —
like saying:
“Hey platform, I expect this function. You give me the actual implementation.”
3️⃣
Platform UI layer
Every platform still uses its native screen-building tools.
This is why KMP is flexible, unlike frameworks that force 100% shared UI.
4. What Can You Build With KMP?
Pretty much everything:
✔ Mobile apps
Android + iOS with shared business logic.
✔ Desktop apps
Using Compose Multiplatform.
✔ Web apps
Using Kotlin/JS.
✔ Full-stack apps
Backend in Ktor + shared models with the mobile app.
✔ Libraries & SDKs
Companies build SDKs once and give to both Android & iOS.
5. What You’ll Learn in This Series
This KMP series will be practical, modern, and beginner friendly.
Here’s what’s coming next:
📚 Next Topic
- Project setup — creating your first KMP project
- Understanding source sets
- Writing shared classes & functions
- Networking using Ktor (shared API service)
- Using SQLDelight for shared database
- Sharing Kotlin models with Serialization
- expect/actual — platform bridging
- Compose Multiplatform basics
- Building a real app with shared logic
Packaging, deployment, and folder structure
Each topic will feel like a real classroom experience — simple, engaging, and step-by-step.
6. Before We Continue…
Whenever you move into KMP, remember one mindset shift:
“I will write platform code only when it actually needs platform features.”
Everything else?
Kotlin handles beautifully across Android, iOS, Desktop, and Web.
⭐ Final Words for Today
KMP is not just another framework.
It’s a philosophy —
a way to stop repeating yourself, start building smarter, and think beyond one platform.
If you learn Kotlin Multiplatform in 2025, you’re learning the technology that’s shaping the next decade of multi-platform development.
In the next Topic, we’ll start setting up your first KMP project and understand the architecture clearly.