View on GitHub

AozoraEpub3-JDK21

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

AozoraEpub3-JDK21 Download

Latest: v1.6.1-jdk21 (August 27, 2026) | Release Notes

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

📋 View all releases

What’s New in v1.6.1-jdk21

New setting: replace gaiji your device cannot display with a readable note. A JIS level-4 character such as 𢌞 shows up as ? or a tofu box when the device font has no glyph for it. With this setting on, the character is replaced by a note that says what it is, like 〓（「廴＋囘」）. It is off by default — leave it alone and your output is byte-for-byte what it was before. The setting lives in the “Gaiji” box on the “Style” tab (how to use it)
Kana with a dakuten mark stay as they are when a bundled font can render them. Annotations such as ※［＃半濁点付き平仮名か、1-4-87］ turn into two characters (a kana plus a combining mark), which the bundled dakuten fonts or CSS stacking can display. These are now judged as a pair: kept whole when they can be rendered, replaced as a whole when they cannot
New page on gaiji settings: which JIS level to pick, where to put single-character fonts (gaiji/*.ttf), and the format of the notes

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). 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