Reducing Flutter App Size

Contents

• Core Concepts
• Workflow: Generating Size Analysis Files
• Workflow: Analyzing Size Data in DevTools
• Workflow: Estimating iOS Download Size
• Workflow: Implementing Size Reduction Strategies
• Examples

Core Concepts

• Debug vs. Release: Never use debug builds to measure app size. Debug builds include VM overhead and lack Ahead-Of-Time (AOT) compilation and tree-shaking.
• Upload vs. Download Size: The size of an upload package (APK, AAB, IPA) does not represent the end-user download size. App stores filter redundant native library architectures and asset densities based on the target device.
• AOT Tree-Shaking: The Dart AOT compiler automatically removes unused or unreachable code in profile and release modes.
• Size Analysis JSON: The --analyze-size flag generates a *-code-size-analysis_*.json file detailing the byte size of packages, libraries, classes, and functions.

Workflow: Generating Size Analysis Files

Use this workflow to generate the raw data required for size analysis.

Task Progress:

• Determine the target platform (apk, appbundle, ios, linux, macos, windows).
• Run the Flutter build command with the --analyze-size flag.
• Locate the generated *-code-size-analysis_*.json file in the build/ directory.