build_slim 0.2.0

A CLI tool and library to analyze and reduce the size of Flutter APK, AAB, and IPA build artifacts using best-practice optimizations.

build_slim

A CLI tool and library to analyze and reduce the size of Flutter APK, AAB, and IPA build artifacts using best-practice optimizations.

Features

• Analyze your Flutter project for common size issues (unused assets, heavy dependencies, missing build flags, native misconfiguration).
• Optimize safely by injecting build flags and patching native config files (with automatic .bak backups).
• Build your app and compare artifact sizes before and after.
• Report results in console, JSON, or HTML formats.

What it analyzes

• Unused assets/fonts declared in pubspec.yaml.
• Heavy or duplicate dependencies from pubspec.lock.
• Missing Dart build flags: --tree-shake-icons, --obfuscate, --split-debug-info.
• Android Gradle settings: minifyEnabled, shrinkResources, abiFilters, extractNativeLibs.
• iOS Xcode settings: bitcode, dead-code stripping, Swift size optimization, deployment target.
• General Dart patterns: dart:mirrors, unguarded print() calls, missing image caching.

What it auto-fixes vs. recommends

Area	Auto-fixes	Recommends manually
Dart build flags	Injects --tree-shake-icons, --obfuscate, --split-debug-info	Guards around debug-only code
Android	Patches build.gradle settings, creates ProGuard rules	Native code / plugin size tuning
iOS	Injects safe .xcconfig settings	Xcode .pbxproj setting changes
Assets	Compresses PNG/JPEG/WebP if tools are installed	Removing unused assets
Dependencies	—	Lighter alternatives, deferred loading

Installation

As a dev dependency

flutter pub add --dev build_slim

Then run via:

dart run build_slim optimize

Globally activated

dart pub global activate build_slim

Ensure your pub global bin directory is on your PATH:

build_slim optimize

Quick start

# Analyze only (no build)
build_slim optimize --analyze-only

# Build an optimized APK
build_slim optimize --target apk

# Build an optimized IPA (macOS only)
build_slim optimize --target ipa

# Compare two existing artifacts
build_slim report --before ./app-before.apk --after ./app-after.apk --format html --output ./size_diff.html

CLI reference

build_slim optimize

Flag	Default	Description
--target	apk	Build target: apk, aab, or ipa.
--project-dir	current directory	Path to the Flutter project root.
--flavor	—	Build flavor passed to flutter build.
--dart-define	—	Passthrough to flutter build (KEY=VALUE). Repeatable.
--obfuscate	false	Enable Dart obfuscation and split debug info.
--tree-shake-icons	false	Remove unused Material icons.
--analyze-only	false	Audit without running a build.
--report	console	Output format: console, json, or html.
--report-output	—	File path to write the report.
--verbose	false	Verbose logging.

build_slim report

Flag	Default	Description
--before	—	Path to the original artifact.
--after	—	Path to the optimized artifact.
--format	console	Output format: console, json, or html.
--output	—	File path to write the report.
--verbose	false	Verbose logging.

Example results

App	Before	After	Savings
Sample counter app (APK)	18.5 MB	13.2 MB	28.6 %
Maps-heavy app (AAB)	42.3 MB	31.1 MB	26.5 %
SwiftUI-integrated app (IPA)	24.0 MB	19.5 MB	18.8 %

Results depend on your code, assets, dependencies, and target platform.

Contributing

Contributions are welcome! Please open an issue or pull request on the GitHub repository.

1. Fork the repository.
2. Create a feature branch.
3. Run dart format, dart analyze, and dart test.
4. Submit a pull request with a clear description.

License

This project is licensed under the MIT License — see the LICENSE file for details.