OpenNH-Download

A Chrome extension that bulk-downloads nhentai galleries into a ZIP archive — one click, zero hassle.

---

✨ Features

• 📦 One-click ZIP download — entire gallery packed and saved automatically
• 🔄 Auto-loops from page 1 to the end, stopping at the first 404
• 🌐 CDN-aware — reads the real image server (i1, i2, i3… subdomains) directly from the page DOM, no guessing
• 🏷️ Named after gallery code — ZIP file is saved as {gallery-id}.zip
• 🖼️ Padded filenames — images saved as 0001.jpg, 0002.jpg… for correct ordering
• 🚫 Cancel anytime — stop mid-download and nothing is saved
• ⚡ Zero dependencies — pure JS, no external libraries, built-in ZIP engine

---

📸 Screenshots

Ready State	Downloading	Done

---

🚀 Installation

Chrome Web Store listing coming soon. For now, install manually:

Step 1 — Download

Grab the latest release ZIP from the Releases page and extract it.

Step 2 — Load into Chrome

1. Open Chrome and navigate to chrome://extensions/
2. Toggle Developer mode on (top-right corner)
3. Click Load unpacked
4. Select the extracted OpenNH-Download folder

Step 3 — Use it

1. Open nhentai.net and navigate into any gallery reader
2. Wait for the page to fully load
3. Click the OpenNH-Download icon in your toolbar
4. Hit ⬇ Download ZIP
5. The ZIP downloads automatically when done

---

🧠 How It Works

nhentai.net/g/177013/1/          ← you open this reader page
        │
        │  executeScript() injects scrapeImageSrc() into the page
        │
        ▼
i3.nhentai.net/galleries/177013/1.jpg   ← real CDN URL read from <img> src
        │
        │  strip page number → extract base URL + CDN subdomain
        │
        ▼
base: https://i3.nhentai.net/galleries/177013/
        │
        │  fetch loop: 1.jpg → 2.jpg → 3.jpg → ... → 404 (stop)
        │
        ▼
  ZipBuilder packs all Uint8Array buffers
        │
        ▼
  177013.zip  ← downloaded to your machine

The key insight: nhentai serves images from numbered CDN subdomains (i1, i2, i3, i5…) that vary per gallery. Rather than guessing which one, the extension reads the src of the image already loaded on the page — giving us the exact correct server every time.

---

📁 File Structure

OpenNH-Download/
├── manifest.json      # Chrome Extension Manifest v3
├── popup.html         # Extension popup UI
├── popup.js           # URL scraping, download loop, ZIP trigger
├── zipper.js          # Built-in ZIP builder (CRC-32, no deps)
├── icon16.png
├── icon48.png
├── icon128.png
└── README.md

---

🔒 Permissions

Permission	Why
activeTab	Read the current tab's URL to detect nhentai
scripting	Inject scrapeImageSrc() into the page to grab the real CDN image URL
downloads	Trigger the ZIP file download
host: *.nhentai.net	Fetch images from all nhentai CDN subdomains

No data is sent anywhere. Everything runs locally in your browser.

---

⚠️ Known Limitations

• Only works while on the reader page (nhentai.net/g/XXXXXX/1/), not the gallery overview
• The page must be fully loaded before opening the popup
• Very large galleries may take a moment to pack — the progress bar will show you

---

🛠️ Development

Clone the repo, make your changes, then reload the extension in chrome://extensions/ using the refresh button.

git clone https://github.com/myrachane/OpenNH-Download
cd OpenNH-Download
# Edit files, then reload in chrome://extensions/

No build step required — it's plain HTML, CSS, and JS.

---

Made with ♥  ·  MIT Licensed  ·  PRs welcome