X4 EPUB Optimizer - WEB Tool

As most of you have probably noticed our beloved X4 doesn't support progressive images and due to ram constraints it never will entirely. That leads to some covers and images not showing up despite image support in 1.1.1 CrossPoint.

**About a month ago I posted my first proof of concept Calibre plugin to help us optimize EPUBs for the X4. The project has evolved quite a bit since then. I decided to focus on a web version. Unfortunately reddit hates cloudflare links, but it's visible on the screenshot.**

# How it works

* You **drag & drop one or multiple EPUB files** * The tool extracts all images from the EPUB * Each image is converted to **baseline JPEG** * The EPUB is rebuilt and downloaded automatically

**Everything runs entirely in your browser — no files are uploaded anywhere.**

# Key features

* **Batch processing** You can drop multiple EPUB files at once and process them in a single run. * **Baseline JPEG conversion** Ensures maximum compatibility with the X4 * **Grayscale conversion** Reduces file size and improves contrast. * **SVG image fixes** Unwraps SVG so they display correctly on devices that don’t support SVG wrap. * **Advanced splitting / rotating function** \- allow you to maximize X4 screen usage. You can pick between Clockwise, Counter Clockwise and Vertical Split. Individual choice for every picture * **Fix** basic errors in EPUB structure (NCX, OPF)

# Status & feedback

This is a personal project and completely free. I’m sharing it as-is, but I’m very open to:

* Bug reports * Feature requests * Workflow ideas * Edge cases you’ve run into with EPUBs

If this helps even a few people, that’s already a win for me.

Thanks for checking it out, and feel free to ask questions or suggest improvements!