Font Conversion for App Developers

Custom typography is essential for creating branded, distinctive mobile applications. While system fonts like San Francisco (iOS) and Roboto (Android) provide excellent readability, custom fonts allow apps to express unique brand identities and create memorable user experiences. In 2026, both major mobile platforms have mature support for custom fonts, though the implementation details differ.

This guide covers font conversion and integration for native iOS and Android development, as well as popular cross-platform frameworks like React Native, Flutter, and Xamarin. You'll learn which font formats work best, how to optimize fonts for mobile performance, and common pitfalls to avoid.

Whether you're building a native Swift app, a Kotlin Android application, or a cross-platform solution, understanding font conversion ensures your typography renders consistently across all target devices.

iOS Custom Font Integration

iOS supports both TrueType (TTF) and OpenType (OTF) fonts. Apple recommends OTF for its advanced typographic features, but both formats work reliably. iOS does not support web font formats like WOFF2—you must convert web fonts to TTF or OTF before use.

// Swift - Using custom font
let customFont = UIFont(name: "BrandFont-Regular", size: 16)

// SwiftUI
Text("Hello World")
    .font(.custom("BrandFont-Regular", size: 16))

For detailed iOS font guidelines, see Apple's Custom Font Documentation.

Android Custom Font Integration

Android also supports TTF and OTF fonts. Since Android 8.0 (API 26), the platform has included Fonts in XML, making it easier to define font families with multiple weights and styles. For older Android versions, you can still use fonts programmatically.

<!-- res/font/brand_font.xml -->
<?xml version="1.0" encoding="utf-8"?>
<font-family xmlns:android="http://schemas.android.com/apk/res/android">
    <font android:fontStyle="normal"
          android:fontWeight="400"
          android:font="@font/brand_font_regular"/>
    <font android:fontStyle="normal"
          android:fontWeight="700"
          android:font="@font/brand_font_bold"/>
</font-family>

<!-- Using in layout -->
<TextView
    android:fontFamily="@font/brand_font"
    android:text="Hello World" />

Learn more in the Android Fonts in XML guide.

Cross-Platform Framework Font Integration

React Native

React Native requires fonts to be linked to your project. Create an assets/fonts folder, add your TTF/OTF files, and configure linking in your react-native.config.js file.

// react-native.config.js
module.exports = {
  assets: ['./assets/fonts'],
};

// Run linking
npx react-native-asset

// Usage in styles
const styles = StyleSheet.create({
  text: {
    fontFamily: 'BrandFont-Regular',
  },
});

Flutter

Flutter uses the pubspec.yaml file to declare fonts. Add your font files to an assets/fonts directory and register them in the pubspec.

# pubspec.yaml
flutter:
  fonts:
    - family: BrandFont
      fonts:
        - asset: assets/fonts/BrandFont-Regular.ttf
        - asset: assets/fonts/BrandFont-Bold.ttf
          weight: 700

// Usage in Dart
Text(
  'Hello World',
  style: TextStyle(fontFamily: 'BrandFont'),
)

See the Flutter fonts cookbook for more details.

Mobile Font Optimization

Font files directly impact your app's download size and launch time. A typical font family with Regular, Italic, Bold, and Bold Italic weights can add 400-800KB to your app bundle. Optimization is essential for maintaining acceptable app sizes.

Common Issues and Solutions

Recommended Tools

Related Use Cases