Comparison
Publ vs Thorium
A focused editorial annotation app, alongside the flagship Readium-based ePub reader.
Thorium Reader is the reference Readium- based desktop ePub reader from EDRLab. It is open source, cross-platform, accessibility-first (TTS, dyslexia fonts, screen reader support), and one of the few readers that handles LCP-protected library lending, audiobooks, and fixed-layout ePubs well. If your priority is reading ePubs, Thorium is the answer.
Publ is a focused tool for a different job: editorial review and annotation. You open an ePub in your browser, highlight passages, drop pins on images or blank page regions, write notes, reply to other reviewers, and export everything as a single self-contained notes file to email to whoever edits the source. Every annotation also captures a screenshot of the surrounding paragraph, so notes survive the ePub being re-exported between drafts. Publ is the ePub app for the editorial review step.
Think of it as: Thorium reads ePubs better; Publ shares ePub feedback better. They are complementary — and a v2 release of Publ is planned to import Thorium's W3C .annotation files so existing Thorium notes can move into the review workflow.
Side-by-side
| Feature | Thorium | Publ |
|---|---|---|
Polished long-form ePub reading experience Publ reads via foliate-js; fine, not flagship. | ✓ | ◐ |
Strong accessibility (TTS, dyslexia fonts, screen reader) Publ: keyboard navigation + themes only. | ✓ | ◐ |
LCP-protected ePub support (library lending) | ✓ | ✗ |
Fixed-layout ePubs (graphic novels, children's books) Publ: deferred to v2. | ✓ | ✗ |
Audiobooks (Readium Web Publications) | ✓ | ✗ |
Open ePubs and read offline | ✓ | ✓ |
Highlight text in colours Publ: 5-colour palette. | ✓ | ✓ |
Write notes on a highlight | ✓ | ✓ |
Bookmarks Publ: location pins double as bookmarks. | ✓ | ✓ |
Pin notes to an image or blank page region | ✗ | ✓ |
Capture a screenshot of each annotation Anchor-block JPEG, survives ePub re-export. | ✗ | ✓ |
Reply threads for multi-reviewer handoff | ✗ | ✓ |
Export annotations as a single shareable file Thorium: W3C .annotation. Publ: JSON with screenshots embedded. | ✓ | ✓ |
Markdown report bundle for the typesetter | ✗ | ✓ |
Browser-based, no install | ✗ | ✓ |
Works offline Publ: PWA, after first load. | ✓ | ✓ |
Files stay on your device (no upload) | ✓ | ✓ |
Free | ✓ | ✓ |
Open source Thorium: BSD-3 / EUPL. Publ: proprietary, free in browser. | ✓ | ✗ |
supported partial not supported
When to use which
- Use Thorium for long-form reading, accessibility-critical workflows (TTS, screen reader, dyslexia fonts), LCP-protected library books, audiobooks, and fixed-layout ePubs. It is the best free desktop reader in this space.
- Use Publ when an ePub is being reviewed before re-export — by an editor, proofreader, indie author, beta reader, or a passing collaborator — and the review needs to ship somewhere as a shareable notes file plus a Markdown report bundle for the typesetter.
- Use both when accessibility matters during reading and the review needs the editorial annotation workflow: read in Thorium, annotate in Publ, share the notes file.
How a review actually flows
- Author / typesetter exports a review build of the ePub from their editor (Sigil, Calibre, Vellum, InDesign).
- Reviewer opens that ePub in Publ, in the browser. No install, no upload.
- Reviewer highlights, pins notes on images and blank regions, writes comments, and (if other reviewers have already weighed in) replies to existing threads. Every annotation captures an anchor-block screenshot.
- Reviewer exports a single notes file and emails it to the next reviewer or the author.
- Author opens the notes file as a Markdown report bundle (one zip; report inside, screenshots in a sibling folder) and applies fixes in their editor of choice.
- Author re-exports. CFI anchors break across re-exports; the captured screenshots give the next reviewer a stable visual reference even when the text has moved.
Common questions
Is Publ a Thorium replacement?
No. Thorium is the flagship Readium-based desktop reader from EDRLab — accessibility-first, supports LCP-protected library lending, audiobooks, and fixed-layout ePubs. Publ does none of those. Publ is a focused editorial annotation and review tool that runs in a browser; reading polish is not its strength.
Can Thorium do everything Publ does?
Thorium supports highlights, notes, and bookmarks, and exports annotations as W3C Web Annotation .annotation files. It does not capture screenshots for each annotation, pin notes on images or page regions, thread replies between reviewers, or generate a Markdown report bundle for the typesetter. Publ is built around those review-specific workflows.
Can I import my Thorium annotations into Publ?
Not in v1. Read-only import from Thorium .annotation files (and Calibre exports) is planned for the v2 release. Thorium's format already uses TextQuoteSelector, which is the same resilience model Publ relies on, so the mapping is straightforward.
Why use a browser for annotation if Thorium runs on my desktop?
No install, easier to open on a colleague's machine or a borrowed laptop, and the notes file is a single attachment you can email. Files still stay on your device — Publ does not upload your ePub. Thorium remains the better experience for long-form reading; Publ is the better experience for review handoff.
Does Publ support accessibility features like Thorium?
Not at Thorium's level. Thorium is built around accessibility — TTS, dyslexia fonts, screen reader support, full keyboard navigation. Publ is keyboard-navigable and theme-aware (light/dark/sepia) but is not yet a first-class accessibility reader. If reading accessibility is a primary requirement, use Thorium to read and Publ for the review step.
Is Publ open source like Thorium?
No. Publ is proprietary (© Quaal Ltd.) but free to use in the browser. Thorium is open source under BSD-3 / EUPL. A paid Publ tier with optional cloud sync and integrations is on the roadmap; the browser annotation core stays free.
Ready to annotate an ePub?
Publ is independent of Thorium Reader. Thorium Reader is developed by EDRLab and distributed under BSD-3 / EUPL. Trademarks belong to their respective owners.