Reflowable text, and the things that break it
There is one idea to absorb, and everything else follows from it: an ebook has no pages.
Not "has flexible pages." Has none. The reader picks the typeface, the size, the line spacing, the margins and the background color. The device then works out where each line ends and where the screen has to break, and it redoes that arithmetic every time the reader rotates the tablet or bumps the type up a notch. A page in an ebook is a temporary event, computed on the device, different for every reader and often different for the same reader an hour later.
That has a blunt consequence. Every layout decision you make in print terms is a decision the reader will overrule. Not might — will, by default, because the reader's settings win and yours are a suggestion the format has no way to enforce.
What breaks
All of these work in your word processor, and all of them come apart on somebody's screen.
- Hard page breaks used as spacing. A page break inserted to push a chapter title down the page produces a gap of unpredictable size on one device and no gap at all on another. Sometimes it produces a blank screen the reader swipes past looking for the missing text.
- Blank lines standing in for a scene break. Three empty paragraphs mean "time passes" to you and mean nothing to the file. Readers that strip empty paragraphs delete your scene break outright; readers that keep them produce a hole that lands mid-screen.
- Manual line breaks inside a paragraph. You pressed return to stop a line running long. At the reader's size that break falls somewhere else entirely, and the paragraph arrives as ragged nonsense — a short line, a long line, a stray word alone.
- Tabs and spaces used as indents. An indent has to be a property of the paragraph. Typed spaces are characters: they scale with the type, wrap with the text, and can leave a line beginning with a gap for no reason.
- Tables used for layout. A table whose job is to place two things side by side has no way to do that on a narrow screen. It squeezes past legibility or scrolls sideways, and either way the arrangement you were relying on is gone.
- Centered text that wraps. A centered title is fine until it is too long for the screen, at which point it breaks into two centered lines with the break in a place you did not choose — usually between an article and its noun.
- Anything positioned by eye. If you nudged it until it looked right, you were measuring against a page width that does not exist on the reader's device.
The pattern is the same throughout: you encoded an appearance, and the format only carries meaning.
What survives: structure
Structure is the part of your file that describes what something is rather than how it should look. It survives because the reading system regenerates the appearance from it, at whatever size the reader has chosen.
- A heading marked as a heading. That is what builds the navigation and what a screen reader announces as a chapter. A line you made bigger and centered is not a heading; it is a big centered paragraph.
- An italic marked as an italic. Emphasis is meaning and travels intact. Emphasis faked by changing the font does not.
- A scene break marked as a scene break. One consistent marker — a centered ornament or a line with a symbol on it — rather than empty space. It then renders as a break on every device, at a size the device picks.
- An image with its caption attached to it. Bound together, they move together. Left as a picture with a nearby paragraph, they drift apart on a narrow screen.
- A declared language, and alt text on every image. Invisible to you and load-bearing for the reader using speech, and the basis of Accessible ebooks, and why they are now everyone's problem.
In the Interior Formatter. It reads a .docx and keeps structure only — chapter starts, italics, bold, scene breaks — then builds the reflowable EPUB 3 and the print PDF from that same structured source. The EPUB carries accessibility metadata, a declared language, ARIA roles and chapter numbering, and validates with zero errors and zero warnings under epubcheck. Start a book → · about the Interior Formatter
The two genuinely hard cases
Most of a novel reflows without argument. Two things do not.
Poetry. Here the line breaks are the content, so the one thing reflow does freely is the one thing you cannot allow. Verse has to be marked as verse, line by line, so that each line is a line rather than a paragraph that happens to be short. The unavoidable problem is the runover: a line too long for the screen has to go somewhere, and the convention is to indent the continuation so a reader can see it is the tail of the line above rather than a new one. Test it at the largest type size a device offers, because that is where every line becomes a runover. Setting poetry without wrecking it covers the print half of the problem.
Anything tabular. A genuine table — data in rows and columns, where the grid carries the meaning — has no good reflowable form on a phone. The usable options are to keep it small enough to survive a narrow screen, to restructure it as a list where each row becomes a short labeled block, or to supply it as an image with the full content written into the alt text. Shrinking it is the option that fails. Tables, charts and data in a printed book is the print counterpart.
Fixed layout is not the answer for a novel
There is a fixed-layout kind of EPUB where the page is frozen, and it is the right format for a picture book or a comic, where the arrangement is the content. For a book that is words in a row it is a bad trade: the reader loses type size control, which is the accommodation most of them depend on, and a page designed for a tablet arrives on a phone as something to pinch and pan. Fixed layout: when the page is the design sets out the whole test.
The habit that fixes most of it
Stop describing appearance in the manuscript and start naming things. A chapter title is a heading. A scene break is a scene break. An indent is a paragraph setting. A quotation is a quotation.
Do that and the ebook and the print interior can both be generated from the same file, and neither is made from the other — which is the point of EPUB and print PDF are two different books. Then open the finished file on a phone at the largest type size you can set. Almost everything still broken is visible in ten minutes there.
Make yours
Everything here is built into the tools, and they are free to use: name your book, bring your manuscript or your artwork, and work as long as you like. You only pay when you want the files without the preview watermark.
Next: What makes an EPUB pass validation · More: EPUB and print PDF are two different books · Preparing a manuscript that typesets cleanly · Checking an ebook before you publish it