r/ePub

epubcheck (https://github.com/w3c/epubcheck) is the de-facto EPUB validator — but it's Java, so embedding it in a web app or a lightweight pipeline means shipping a JVM. I've been building epubveri: a validator written entirely in Rust (no C dependencies), with a WebAssembly build that validates EPUBs directly in the browser — no JVM, no server, nothing leaves the page.

What it does

- Hand-coded structural checks (OCF/mimetype, OPF metadata, manifest/spine integrity, broken references, nav docs) plus RELAX NG / XPath / Schematron engines for the XHTML/SVG content model.

- Reuses epubcheck's message IDs (RSC-…, OPF-…, HTM-…) so the output is familiar to existing toolchains.

Honest status (measured, not vibes)

Against epubcheck's own test corpus, it currently hits 98.8% exact-message-ID recall on the should-error cases, with ~1% false positives on the valid cases. It's pre-1.0 and not a full drop-in replacement yet — the deepest content-model edge cases and some niche rules are still a climb. But it's fast, embeddable, and already catches real problems in real books.

Just shipped

- WASM package on npm: u/veripublica/epubveri-wasm (validate client-side)

- crates.io name reserved; the functional Rust crate follows once a dependency lands

Code: https://github.com/veripublica/epubveri

Dual-licensed (AGPL-3.0 or commercial). Feedback, bug reports, and especially weird real-world EPUBs that break it are very welcome.

Hey everyone — I built Books Whisper, a free web-based EPUB reader focused on making reading easier to continue when you don’t feel like staring at the page.

Link: https://bookswhisper.com/

What it does:

• Upload and read EPUB books for free
• Organize books with collections, loved/completed status, search and filters
• Listen to books with built-in text-to-speech
• Click a paragraph to start audio from there
• Highlight the current passage while audio plays
• Auto-scroll while listening
• Take private notes tied to sections/passages
• Light/dark themes and adjustable text size

The idea came from wanting something between a simple EPUB reader and an audiobook app — especially for people who already have EPUBs but want a way to keep reading/listening without switching tools.

I’d love feedback on the landing page, the value proposition, and which reader/listening features you’d expect before using it regularly.

Logseq stores everything as plain .md files, but if you ever open one of those files directly on iOS (from Files, iCloud, Dropbox, a backup, etc.) you just get raw text. I built a small viewer to read them rendered on a phone.

Md Preview:

• Renders GitHub-Flavored Markdown — headings, tables, task lists, footnotes

• Code blocks with syntax highlighting, plus LaTeX math and Mermaid diagrams

• Opens .md / .markdown / .mdx / .rmd / .qmd from Files or the Share Sheet

• 100% on-device — no account, no uploads, no ads, no subscriptions

Free on the App Store: https://apps.apple.com/app/id6760341080

Details: https://markdown.cybergame.ai/

Not a Logseq replacement at all — just a quick way to read loose .md files when you're away from the desktop app. Curious how you all read your graph on the go.

KCC 10.3.0 has a new feature: light novel support!

Light novels and other illustration heavy EPUBs sold from distributors like Humble Bundle and Fanatical often include extremely high quality and high resolution images in EPUBs they sell. In this example, the EPUBs are up to 40 MB each.

By just downscaling to the screen resolution of the Kindle Paperwhite 12th Gen in this example, file sizes can be reduced to as low as 4 MB, so you can fit a lot more of them on your device!

You can also optionally change the JPEG quality factor or force grayscale conversion using the options. All the other option checkboxes are ignored since those are only for fixed layout comics/mangas instead of normal reflowable epub books. The new light novel mode preserves the original file's file structure.

- the kcc dev

Epublys — what changed since I last posted it here

Quick reminder of what it is: Epublys is a free EPUB toolkit that runs in your browser. You can merge, split, compress, convert to and from PDF, edit metadata, validate and read your books, with no install and no account for the core tools. Files are processed in memory and never stored anywhere.

I've put a lot of work into it since the first post, so here is where it stands now:

• You can read both EPUB and PDF directly in the browser, with a real table of contents, search and bookmarks. It now keeps your theme and font size from one book to the next. Sounds small, but I missed it myself.

• The validator doesn't only tell you what's wrong, it fixes the most common problems in one click. If you publish on Amazon KDP or Apple Books, run your file through it first, it catches the structural things that usually get books rejected.

• Converting between EPUB and PDF gives you clean files with no watermarks.

• There is an AI cover generator if you need a cover. You describe the book, it generates one, and you apply it to your EPUB without leaving the page. This one is part of the paid tier, which you don't need to use but I'll appreciate support to keep this ads free forever.

• You can process a whole batch of files at once and download everything as a single ZIP.

• It's faster than before and works properly on mobile.

And a lot of smaller things across every tool that I won't list one by one.

About the paid side: if you want to support the tool, feel free to subscribe. If you don't, that's completely fine too. We still managed to deliver more than 2,000 EPUB operations over the last 3 months, and the free tools are not going anywhere.

The thing I'd genuinely like to know is this: what is the EPUB problem you keep running into that no tool handles well? That's what I want to build next.

epublys.com

Hi r/ebooks 👋

Like a lot of you, I've got a library full of EPUBs collected over many years — and some of the older ones are a bit of a mess. They open awkwardly on newer readers, the navigation/table of contents is clunky, and a few are way bigger than they need to be because of heavy images.

So I built a little tool to fix that, and figured some of you might find it useful too. It's called ePubLift, and it's free and open source.

What it does to a book:

- Brings it up to date. It upgrades older EPUB 2.0 files to the modern EPUB 3.3 format — rebuilding the navigation/table of contents properly and cleaning up outdated markup.

- Keeps it working everywhere. The upgraded book stays backward-compatible, so it still opens fine on older e-readers, not just new ones. You don't trade compatibility for modernization.

- Makes it smaller. It re-encodes the images inside to a more efficient modern format (WebP), which often shrinks the file noticeably without you having to do anything.

- Won't ruin your originals. It always works on a copy — your source file is never modified unless everything succeeds. The book's title and author come from inside the file, so they stay exactly as they were.

A couple of honest caveats: right now it's a command-line tool, so it's most comfortable if you're okay running a command in a terminal. A simple drag-and-drop app is on my to-do list for folks who'd rather not. And it focuses on upgrading and optimizing existing EPUBs — it's not a converter between formats like Calibre.

It's completely free, open source (AGPL-3.0), and there's a public roadmap if you want to see where it's headed.

Here it is if you'd like to try it: https://github.com/ePubLift/epublift

I'd love to hear what you think, and if it makes a few of your books nicer to read, that'd make my day. 🙂