Text is the star: reflowable. Pictures and layout are the star: fixed layout.
What matters here is that neither one is better than the other. They exist for different purposes, and picking the wrong one produces a book that is hard to read.
Reflowable is the basic form of EPUB. Unless you say otherwise, an EPUB is reflowable.
The text is written in HTML and the reading app pours it onto the screen. "What is on page 12" is not decided in advance. If a reader enlarges the type on a phone, the page count simply grows. Turn a tablet landscape, and the number of characters on screen changes.
If you are used to paper it can feel strange, but the idea is that the book adapts to the reader. Someone who cannot read small type and someone reading on a phone during their commute get the same file, and both are comfortable.
Fixed layout is built as "one page = one HTML file". You decide the width and height of each page and place images or text on it.
The "this is fixed layout" declaration goes into the file that holds the book’s details, content.opf .
And the HTML of each page states the page size.
For manga or a photo book, each of those pages usually holds nothing but a single image.So a fixed-layout EPUB is, in effect, "images pasted one per page and bound together" — that is a useful way to picture it.
When you want two pages shown side by side — a manga spread — you use the rendition:spread setting. Reading apps interpret it differently, though, so whether they line up as you intended varies by environment.
This is the part of the article I most want to get across.
In a fixed-layout book, the contents of a page are usually an image. And if it is an image, the text drawn on it is part of the picture — to a machine it is not text at all.
Which leads to this.
| Reflowable | Fixed layout | |
|---|---|---|
| Changing type size | Yes | No |
| Searching the text | Yes | No |
| Read-aloud | Yes | No |
| Dictionary lookup | Yes | No |
| File size | Small | Tends to be large |
Type that cannot be enlarged means the book becomes unreadable for a reader with weak eyesight or an older reader. The same goes for anyone who relies on read-aloud.
There are of course books — manga, photo books — where fixed layout is the only option. But making a text book fixed-layout just because "the design will not shift" costs you readers.
International standards for EPUB accessibility exist, and who can actually read an ebook is a point the whole industry now takes seriously.When in doubt, choose reflowable — from this angle, too, that is the sound call.
The decision is not hard. These criteria settle almost every book.
If the call is close, ask yourself this.
"If one character shifted position, would the work suffer?"
If yes, fixed layout; if no, reflowable. A novel reads the same wherever the lines break, but a picture book is ruined if the text slides off the art. That difference is exactly the difference between the two shapes.
Fixed layout is not an upgrade over reflowable. It is a mechanism that guarantees appearance in exchange for taking capabilities away. As the table above shows, readers can do less, not more.
Reflowable and fixed layout differ in how the insides are built. Treat them as different from the manuscript stage onward. "Build it and change it later" is essentially not an option.
The specification does allow a reflowable body with a few fixed-layout pages. Support varies from app to app, though, so if it must read reliably, sticking to one is safer.
Make a manga into a fixed-layout EPUB and the pages do display correctly. But features like zooming panel by panel on a phone depend on each reading app’s own implementation. Building the file correctly does not guarantee the same reading experience everywhere — worth keeping in mind.
EPUB FACTORY handles both reflowable EPUB from a text manuscript and fixed-layout EPUB from images. No account, no installation.
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