EPUB refers to a reflowable eBook format that adjusts to different screen sizes and reading preferences.
Common Uses
Publishing digital books for e-readers
Creating responsive files for mobile reading
Distributing digital publications
EPUB Transformation FAQ
What is an EPUB file?
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EPUB (Electronic Publication) refers to a free and open eBook standard by the International Digital Publishing Forum.
Why does the same EPUB book look different on two devices?
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Because it is meant to. An EPUB is a package of structured text and styling that the reader lays out at your chosen font and size, so page count and line breaks are properties of the device, not of the book. Converting to a fixed-layout format freezes one particular rendering — good for printing, worse for reading on a phone. EPUB is the open ebook standard from the International Digital Publishing Forum, now maintained by the W3C.
Why do most bookshops hand out EPUB?
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Because it is the open standard everything except Kindle settled on, so one file serves a Kobo, a phone, a tablet and a desktop reader alike. The format itself carries no lock of any kind. What a shop may add on top is a separate encryption layer tied to your account — that is the shop's wrapper rather than part of the format, and it is the whole difference between a file that converts here in seconds and one no converter can open at all.
Why does my purchased EPUB refuse to convert?
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Because it is encrypted. A store-bought EPUB is locked to an account, and the file a converter sees is ciphertext rather than a book — there is nothing to read until the store's software decrypts it for its own reader. Removing that protection is a legal grey area in many countries and is not something this site does. Files you made yourself, or downloaded DRM-free, convert normally. EPUB has no fixed pagination, so page numbers are meaningless, and complex layout — tables, equations, multi-column — degrades badly.
Does the table of contents survive converting an EPUB?
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Yes, wherever the target has somewhere to put it. Ebook formats store navigation as real structure — a list of chapter anchors that the reader turns into a jump menu — and that is carried between them. A fixed-layout export turns it into bookmarks instead, and a plain-text export loses it along with everything else structural. Chapter breaks themselves survive all three.
What if my EPUB is a scan rather than real text?
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Then nothing downstream can read it until OCR has run. A scanned page is a picture of words: it looks fine, and searching, copying or converting to an editable document all come back empty. Optical character recognition adds a real text layer over the image, after which the words are selectable and the conversion produces an actual document instead of a wrapper around a photograph.
Is the cover image kept when I convert an EPUB?
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It is, provided the book records one as the cover rather than merely having a picture on its first page. That distinction is why a converted book sometimes shows a blank placeholder in a library: the image is still inside the file, but nothing marks it as the cover, so the reader app displays nothing. It is metadata rather than content, and it can be set afterwards without touching the text.
Does an EPUB have fixed pages?
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No — content flows, and pages appear only when something decides on a page size. Change the font, the margins or the screen and the page numbering changes with it. That is why a page reference from an EPUB is unreliable, and why converting to a fixed-layout format is the step that makes page numbers mean something.
Is an EPUB really a ZIP archive underneath?
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It is, and renaming a copy and opening it with any archive tool proves it: inside are the structured parts the format is built from, plus the images and fonts they reference. That design is why these files compress well, why a damaged one can sometimes be partly recovered, and why software that is not the original application can read them at all. It is not an invitation to edit the parts by hand — the manifest has to stay consistent. An EPUB is a ZIP archive of XHTML and CSS with a manifest — essentially a small website packaged as a book.
Who controls the EPUB format?
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Nobody, and that is the point of it. The specification is public, anyone may implement it without asking or paying, and no company can change the terms later — which is why archives, standards bodies and public institutions specify formats like this one for anything that still has to open in twenty years. The trade is not compatibility, which is excellent; it is that there is no vendor to call when some tool implements the spec badly.
Can I convert a whole folder of EPUB files in one go?
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With an account, yes — drop them in together and they are queued as one job rather than handled one at a time, with the same settings applied across the batch and the results returned together. Free conversions run a single file at a time (merge tools take two); a paid plan is what unlocks batch processing and the larger per-file limit, which is what makes converting a whole archive practical.
What happens to my EPUB file after the conversion?
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It is deleted. The upload and the converted result both sit on the server only as long as the job needs them and are then removed automatically; the transfer runs over HTTPS in both directions. Nobody reads the contents, nothing is indexed, and nothing is passed to anyone else. If you would rather not wait for the automatic sweep, closing the job removes the files immediately.
