[TOOL] PureEPUB: Free web tool to convert messy PDFs & EPUBs into native Kobo KePub

[lones]

Hi everyone,

Just registered on MobileRead to share a personal tool I've been building and refining over the past few months.

The project actually started out of frustration: my girlfriend got an e-reader and wanted to read a bunch of books that were only available as messy, badly-formatted PDFs. She didn't want to wrestle with complex settings or desktop software, so I decided to build a dead-simple, zero-friction web tool she could just use directly from her phone or e-reader browser.

I initially shared an early prototype on Reddit r/ebooks about a month ago (link to the Reddit thread). I received great feedback from testers there, and since then I've focused heavily on making the output first-class for Kobo hardware.

The tool is called PureEPUB (https://pureepub.com). It takes messy, hard-wrapped PDFs or raw EPUBs/MOBIs and turns them into clean, native .kepub.epub files.

What it does under the hood for Kobo:

1. Native KePub Span Generation (koboSpan):
Wraps paragraph blocks with valid <span class="koboSpan" id="kobo.X.Y"> markers so Kobo's ACCESS rendering engine properly calculates chapter reading time, page numbers, and instant page turns.

2. Kobo Firmware CSS & Hyphenation:
Injects -webkit-hyphens: auto; hyphens: auto; adobe-hyphenate: auto; rules. It also strips hardcoded font colors and enforces color: inherit !important; so native Kobo Dark Mode / inverted reading doesn't get broken by black text on black background.

3. Screen-Matched Sleep Screen Covers (No Sidebars):
Includes direct resolution presets for Kobo hardware:
- 6.0" (1072 × 1448) — Clara 2E / BW / Colour
- 7.0" (1264 × 1680) — Libra 2 / Colour
- 8.0" (1440 × 1920) — Sage / Forma
- 10.3" (1860 × 2480) — Elipsa / 2E
Offers an Ambient Fill mode: preserves the original cover's native aspect ratio, but fills the letterbox gaps with a soft, darkened Gaussian-blurred version of the cover. Looks clean on sleep screens without harsh black or white bars.

4. Text Reflow & PDF Sanitization:
Extracts via PyMuPDF with a C++ Poppler fallback. Heuristically stitches broken line wraps and severed dialogues across page breaks while keeping real paragraph boundaries, blockquotes, and em-dash dialogue tags intact. Scrubs running headers, repeated watermarks, and severed footnotes.

5. Supported Inputs:
PDF, EPUB, MOBI, AZW3, DOCX, and TXT (handy if you have old Kindle-format books you want to bring over to your Kobo as KePub).

6. Wireless Sideloading via Kobo Browser:
Because it’s completely browser-based, you can navigate to https://pureepub.com directly inside the Kobo's built-in web browser (Beta Features -> Web Browser) and download the .kepub.epub file straight to the device without needing a USB cable.

Privacy & Architecture:
The backend runs purely in RAM. Uploaded files are processed in isolated temporary memory streams and immediately deleted after conversion/download. No user accounts, zero telemetry, no file storage, and 100% free without ads.

Website: https://pureepub.com

I'd really appreciate feedback from regular Kobo users here — especially regarding layout quirks, font rendering, or complex test files that usually trip up converters.

Thanks!