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AozoraEpub3-JDK21

AozoraEpub3 - Aozora Bunko to EPUB 3 Converter (JDK 21)

AozoraEpub3-JDK21 Download

Latest: v1.7.6-jdk21 (October 20, 2026) | Release Notes

📦 Windows (ZIP) 🐧 Linux (TAR.GZ) 🍎 macOS (TAR.GZ)

📋 View all releases

What’s New in v1.7.6-jdk21

Correct title and author when regenerating books: regenerating a Narou or Nocturne work whose author name had no My Page link put the work title in the author field and left only the series name as the title. This has been fixed

See the release notes for the full list.

What’s New in v1.7.5-jdk21

A right-click menu on the shelf: right-click a book card (or press Shift+F10 with the card focused) to open its folder, move the book to the OS trash, and more. On shelves opened from the GUI or CLI, books downloaded from the web can also be regenerated with the current settings or have every episode refetched
Protecting downloaded text during updates: when the site returns a page without episode text (such as a maintenance notice), the update now keeps the cached episode instead of overwriting it

See the release notes for the full list.

What’s New in v1.7.0-jdk21

Aozora Bunko work URLs are converted from the text zip on the book card. Reading the HTML back used to drop emphasis dots, indents, headings and more; now the result is the same as converting the zip directly. The GUI also converts zip URLs instead of only downloading them
Web conversion fixes: comma-separated numbers in the body (1,000円) no longer vanish, and ［＃ in a title or episode title is no longer read as an annotation. Numbers in episode and chapter titles now follow narou.rb
Fixes that change the output: short centered pages in vertical books (chapter title pages and the like) are now really centered, Web conversion puts a page break after a chapter title page, and the running head (柱) on chapter pages is output as narou.rb does
Fixes for stopped conversions and lost text: an unclosed block annotation before the title no longer empties the body, an unclosed ruby or gaiji annotation no longer stops the whole conversion, and one failed book no longer stops a CLI batch

See the release notes for the full list.

See the release list for past changes.

Screenshots

Settings for title, cover and page output, with a drop area for input files — Conversion window (drag and drop a file or URL)

Viewer with a chapter table of contents on the left and vertical multi-column text on the right — Browser preview (table of contents, vertical writing, ruby, multi-column)

You can preview a converted EPUB straight in your browser before moving it to a reader app. The preview shows Night on the Galactic Railroad by Kenji Miyazawa from Aozora Bunko (public domain).

About This Project

This software is a derivative of AozoraEpub3 by hmdev, updated for Java 21–26 compatibility and support for modern operating systems.

It aims to comply with EPUB 3.3 and the Japanese Book Publishing Association (電書協) EPUB 3 Production Guide, validated with epubcheck 5.x.

System Requirements

Java 25 LTS recommended
- Compatible with Java 21 LTS as well (JDK 26 runtime also verified)
- Minimum requirement: Java 21 or later
Windows / macOS / Linux

If you don’t have Java installed, download Eclipse Temurin Java 25 LTS (Java 21 LTS also works).

Install Java 25 (Eclipse Temurin)

Windows

Visit Adoptium Releases
Select JDK 25 → Windows x64 → .MSI
Double-click the MSI file and follow the installer
Verify in Command Prompt: java -version

macOS

Visit Adoptium Releases
Select JDK 25 → macOS → .PKG (Intel or Apple Silicon M1/M2)
Double-click the PKG file and follow the installer
Verify in Terminal: java -version

Linux (Ubuntu/Debian)

Visit Adoptium Releases
Select JDK 25 → Linux x64 → .TAR.GZ
Extract: tar -xzf OpenJDK25U-jdk_x64_linux_hotspot_25_x.tar.gz
Verify: ./jdk-25.x.x+yy/bin/java -version or add to PATH

Quick Start (Windows)

Download the latest ZIP file from Releases
Extract to any folder
Double-click AozoraEpub3.exe to launch
The GUI will open when ready

Note: If double-clicking the JAR file doesn’t work, use the EXE file instead.

Installation (macOS / Linux)

Download the TAR.GZ file from Releases
Extract: tar -xzf AozoraEpub3-*.tar.gz
Navigate to the folder and run: ./AozoraEpub3.sh
If you get a permission error, first run: chmod +x AozoraEpub3.sh

Command Line Usage

For advanced configuration, you can run from the command line:

java -jar AozoraEpub3.jar -of -d out input.txt

To launch the GUI, run without arguments: java -jar AozoraEpub3.jar

See the README for detailed options.

narou.rs Setup Guide (recommended) — Setting up the Rust-based compatible tool narou.rs with AozoraEpub3 (Windows 11, with screenshots). Since v0.4.0 you can also choose the Java-free GPL edition with a built-in conversion engine. Actively updated with feature and security fixes — the better choice if you are starting fresh
narou.rb Setup Guide — Installing the Ruby-based narou.rb and connecting it to AozoraEpub3

Troubleshooting

Java is not installed — Download Java 25 LTS from Temurin and install (Java 21 or later also works).
JAR file won’t open on Windows — Use the EXE file, or launch from Command Prompt with java -jar AozoraEpub3.jar.
“Windows protected your PC” when starting the EXE — This is a SmartScreen warning, not a malware detection. Right-click the ZIP → Properties → tick Unblock before extracting, and it will not appear. Full steps
Permission denied on Linux/macOS — Run chmod +x AozoraEpub3.sh and try again.
narou.rb says Java is not installed, but Java is installed — EPUB output has most likely failed. From v1.3.7-jdk21 the exit code on conversion failure changed from 0 to 1 (an intentional change). See the narou.rb Setup Guide.
Detecting conversion success from a script — The CLI returns 0 on success and 1 on failure. See Exit Codes in the usage guide.
Other issues — Report on GitHub Issues.

GitHub README — Features & detailed settings
EPUB 3.3 Guide — Changes from 3.0 and support status
日本語 — このページを日本語で表示