Frequently Asked Questions
Is Epublys really free?
Yes. All core tools are free with no sign-up required. We plan to offer a Premium tier with higher limits for power users, but the free tier will always exist.
What are the file size limits?
Free tier: 20MB per file, up to 10 files for merge operations. Premium (coming soon): 200MB per file, up to 500 files.
Are my files stored on your servers?
No. Files are processed entirely in memory and are never written to disk or any persistent storage. There is no file to delete because nothing is saved.
What EPUB versions are supported?
Epublys supports both EPUB 2 and EPUB 3 files. The validator checks compatibility with both standards.
Can I convert EPUB to PDF?
Yes. Our EPUB to PDF converter extracts text content and generates a clean PDF with no watermarks. Note that complex layouts (heavy CSS, SVG illustrations) may not transfer perfectly — this is a text-focused conversion.
Does merging preserve formatting?
Yes. The merge tool preserves each book's CSS, images, and chapter structure. It generates a combined table of contents and optional divider pages between books.
Can I use Epublys on mobile?
Yes. Epublys works in any modern browser — desktop, tablet, or phone. No app installation required.
Is there an API?
The same API that powers the web interface is available for programmatic use. All endpoints accept multipart/form-data. Rate limits apply. Documented API access for integrations is on our roadmap.
What happens if processing fails?
You'll see a specific error message. Common causes: corrupted EPUB files, files that exceed size limits, or unsupported EPUB structures. Try validating your EPUB first to check for issues.
How is this different from Calibre?
Calibre is a full desktop ebook manager (great for large libraries). Epublys is a quick online tool for one-off tasks — no install, no learning curve. Read our full comparison.