Kindle Comic Optimizer

Turned a 215 MB CBZ into a readable 22 MB Kindle file using Target Size mode.

Results vary by source pages and target device.

Desktop beta tool for converting CBZ comics into Kindle-friendly files with practical size targets.

Download the latest beta

What It Does

Kindle Comic Optimizer helps prepare comics for Kindle reading by converting a CBZ file into one of these output formats:

• Fixed-layout EPUB for Send to Kindle
• CBZ for archive and comic readers
• PDF
• Kobo KEPUB (.kepub.epub)
• Optimized JPEG page folder

It is built for readers who want smaller, Kindle-ready files without manually testing compression settings page by page.

Available Builds

• Windows x64
• macOS Apple Silicon, M1/M2/M3/M4
• macOS Intel

Beta 0.4 Highlights

• Fast Target Mode estimates the target size from sample pages instead of fully converting the comic at every test setting.
• Multi-core image processing uses up to 8 CPU workers for page conversion.
• Faster archive writing stores JPEG pages directly instead of compressing them a second time inside CBZ or EPUB files.
• Original CBZ files are never changed.
• Source code is available in this repository and can be built with Go.

Quick Start On Windows

1. Download KindleComicOptimizer_Beta_0.4_Windows.zip from the latest release.
2. Extract the ZIP file.
3. Double-click KindleComicOptimizer.exe.
4. Select a CBZ file.
5. Choose Fixed-layout EPUB, CBZ, PDF, KEPUB, or optimized JPEG page folder.
6. Select your Kindle profile.
7. Enter a target size, such as 30 MB.
8. Leave Fast Target Mode checked.
9. Click Convert.

Quick Start On macOS

1. Download KindleComicOptimizer_Beta_0.4_macOS.zip from the latest release.
2. Unzip the download.
3. Move Kindle Comic Optimizer.app to your Applications folder.
4. The first time, Control-click the app, choose Open, then choose Open again.
5. Choose a .cbz comic, output format, device profile, and target size.
6. The converted file is saved next to the original comic.

Notes For Beta Users

Fast Target Mode usually finishes much faster than the previous adaptive target workflow. Because it estimates from sample pages, the final file size can vary slightly from your requested target.

These are unsigned beta builds. Windows SmartScreen may display a warning on Windows. macOS may require Control-click > Open the first time because the app is not code-signed or notarized yet.

Who It Is For

• Kindle users who read comics, manga, graphic novels, or scanned books
• Readers who use Send to Kindle and need fixed-layout EPUB output
• People who want a smaller file while keeping images readable
• Anyone who wants a simple desktop app instead of a command-line workflow

Download

The recommended download is the GitHub release asset:

Works offline. Your comic files stay on your computer and are never uploaded.

• Latest release
• Windows ZIP file
• macOS ZIP file
• SHA256 checksums

Build From Source

The app is written in Go and uses only the Go standard library. Install Go 1.23 or newer, then run:

go build -o KindleComicOptimizer .

Windows build helper:

scripts\build-windows.bat

macOS build helper:

chmod +x scripts/build-macos-app.sh
./scripts/build-macos-app.sh

More source notes are in docs/SOURCE.md, and release QA notes are in docs/RELEASE_CHECKLIST.md.

Feedback And Issues

Beta feedback is welcome. Please open an issue with:

• Your operating system and version
• The output format you selected
• The Kindle profile you used
• The target size you entered
• What happened versus what you expected

Do not upload copyrighted comic files to public issues. If a specific file triggers a bug, describe its size, page count, image type, and output settings instead.

Roadmap Ideas

• More Kindle profiles
• Better final-size prediction
• More detailed conversion progress
• Optional advanced image settings
• Signed and notarized desktop builds

License

Kindle Comic Optimizer is released under the MIT License. See LICENSE.