Comparison
Publ vs Calibre
A focused ePub annotation app, alongside the library manager everyone already uses.
Calibre is the de-facto ePub Swiss army knife: a library manager, format converter, ePub source editor, metadata fixer, e-reader sync tool, and a reader. Most people working with ePubs already use it, and Publ is not trying to replace any of those features.
Publ is a focused tool for one step of the workflow: editorial review. You open an ePub in your browser, highlight passages, drop pins on images or blank page regions, write notes, and export everything as a single self-contained notes file that you 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 that handles the review pass.
Think of it as: Calibre is your library and your editor; Publ is the annotation step between them.
Side-by-side
| Feature | Calibre | Publ |
|---|---|---|
Manage a library of many ePubs Publ is session-based, not a library. | ✓ | ✗ |
Convert between ePub / MOBI / AZW / PDF | ✓ | ✗ |
Edit the ePub source (HTML / CSS / metadata) Publ never modifies the ePub. | ✓ | ✗ |
Send to Kindle / sync to e-readers | ✓ | ✗ |
Open and read ePubs | ✓ | ✓ |
Highlight text in colours Publ: 5-colour palette. | ◐ | ✓ |
Write notes on a highlight | ✓ | ✓ |
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 Publ: JSON file with screenshots embedded. | ◐ | ✓ |
Markdown report bundle for the typesetter | ✗ | ✓ |
Runs in a browser, no install | ✗ | ✓ |
Works offline Publ: PWA, runs offline after first load. | ✓ | ✓ |
Files stay on your device (no upload) | ✓ | ✓ |
Free | ✓ | ✓ |
Open source Publ: proprietary, free in browser. | ✓ | ✗ |
supported partial not supported
When to use which
- Use Calibre when you need to organise a library, convert formats, edit the ePub itself, fix metadata, or push a finished book to a Kindle.
- Use Publ when an ePub is being reviewed before re-export — by an editor, proofreader, indie author, beta reader, or a passing collaborator. Use it alongside Calibre, not instead of it.
- Use both for the full editorial loop: manage and edit the ePub in Calibre, annotate the review build in Publ, email the notes file back to whoever runs the Calibre editor, repeat.
How a review actually flows
- Author / typesetter exports a review build of the ePub from Calibre (or Sigil, 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. Every annotation captures an anchor-block screenshot.
- Reviewer exports a single notes file and emails it to the author / typesetter.
- Author opens the notes file as a Markdown report bundle (one zip; report inside, screenshots in a sibling folder) and applies fixes in Calibre.
- Author re-exports. CFI anchors break across re-exports, but the captured screenshots give the next reviewer a stable visual reference.
Common questions
Is Publ a Calibre replacement?
No. Calibre is a full ePub library manager, format converter, source editor, and reader; Publ does none of those things. Publ is a focused annotation and review tool for the editorial step between writing and re-exporting an ePub. Most workflows that use Publ also use Calibre.
Can Calibre do everything Publ does?
Calibre supports basic highlights and notes in its reader. It does not capture screenshots for each annotation, pin notes to images or page regions, export annotations as a shareable single file with embedded screenshots, generate a Markdown report bundle for the typesetter, or thread replies between multiple reviewers. Those workflows are what Publ is built around.
Why annotate in a browser if Calibre runs on my desktop?
Publ runs in any modern browser with no install, which makes it easy to share a session with a collaborator over a link, or open a notes file on a borrowed machine without installing software. Files still stay on your device — Publ does not upload your ePub.
Can I import my Calibre annotations into Publ?
Not yet. Read-only import from Calibre and Thorium annotation exports is planned for the v2 release. The v1 sidecar format is a Publ-native JSON file with embedded screenshots, designed to round-trip between reviewers.
Is Publ open source like Calibre?
No. Publ is proprietary (© Quaal Ltd.) but free to use in the browser. A paid tier with optional cloud sync and integrations is on the roadmap; the browser-based annotation core stays free.
Ready to annotate an ePub?
Publ is independent of Calibre. Calibre is © Kovid Goyal, GPLv3. Trademarks belong to their respective owners.