Your e-book looks different on every device because most e-books are built as reflowable text. The file carries your words and structure. The device decides how those words appear — line length, page breaks, font size, spacing. That is not a glitch. It is the core design of formats like EPUB.
The trade-off is real. You gain readability on a phone, a tablet, and a six-inch e-reader alike. You lose control over how your pages look. As StoryLoft's knowledge base puts it, readers' settings override many of your formatting choices, so you control structure and hierarchy while readers control appearance.
This guide explains the mechanism, why fixed-layout books behave differently, and the practical fixes that keep a reflowable book rendering cleanly everywhere. If you read mostly on apps rather than dedicated hardware, our Apps coverage picks up the device-side questions this article leaves alone. This connects to our earlier piece, What Privacy Settings Matter in Reading Apps?.
What exactly is reflowable text?
Reflowable text is text that reorganises itself to fit the screen. Change the font size, and the book reflows — lines break at new points, paragraphs stretch or compress, and the text flows to the next page. Rotate the device, and it happens again. The layout is computed at reading time, not baked into the file.
Pressbooks, the book formatting software maker, describes it plainly: with a reflowable e-book, you resize the fonts and the book just reorganises itself, whether you read in portrait or landscape. Text and images fill the page according to the settings you have specified. The file is closer to a set of instructions than to a finished page.
That is why the same novel looks different on a Kindle, an iPad, and an Android phone. Each device interprets the file against its own screen and the reader's own settings. Three readers can open the identical file and see three different books. Readers following this should also see How to Borrow Library E-Books on a Kindle E-Reader.
What can authors actually control?
Less than a print designer would like, and more than most authors fear. The reliable levers are structural:
- Heading styles for chapter titles
- Paragraph styles for consistent spacing and indentation
- Bold and italic for emphasis
- Content order, chapter structure, and table-of-contents navigation
- Inline images that scale automatically
What you cannot control, per StoryLoft's guidance: exact page breaks, line breaks within paragraphs, the font a reader ultimately sees, text size, spacing, and precise image positioning relative to text. The reader's device and preferences win every conflict.
The mindset shift is the whole game. A print manuscript aims at precision. An e-book should aim at structure — a clean hierarchy that adapts gracefully instead of collapsing when a reader bumps the font up two sizes.
Why do fonts and spacing cause so much trouble?
Fonts are the first failure point. When you embed a font, you pack it into the file so readers see what you intended. But platforms handle embedded fonts unevenly, and older devices often ignore custom fonts entirely and fall back to whatever the device offers. A decorative font that looks charming in your manuscript can render as an unreadable substitute on half your readers' hardware.
The practical fix is to build around widely supported fallback fonts. Serif choices like Georgia and Palatino render consistently across most devices; Verdana is a screen-first sans-serif option for non-fiction. Skip the decorative stuff — Papyrus, Brush Script, and their cousins are the usual casualties.
Spacing is the quieter problem. Line height set in fixed pixel amounts breaks when a reader changes font size, because the text scales and the gaps do not. Set line height with relative values instead — roughly 1.3 to 1.5 times the font size is the commonly cited sweet spot — so the spacing scales with the text. And go easy on margins: the device handles most of that, and generous margins in your file stack on top of the device's own, squeezing your text into a narrow column.
What about images?
Images are where reflowable formatting bites hardest, because images do not reflow. Text adjusts when a reader changes font size or rotates the screen. Images either stay the same size, stretch awkwardly, or overflow small screens.
The working rules, as laid out by AlphaEbook's guide to e-books that look broken across devices: size images at 100% width maximum so the e-reader scales them to the reading area; use JPEG for photographs and PNG for graphics with sharp edges or text; include alt text, which screen readers depend on and many distribution platforms require. Avoid fixed-width images and text baked into images — the latter becomes unreadable when scaled, so recreate anything important as real text.
Complex infographics deserve special scepticism. They work in print and routinely fail in reflowable e-books. Break them into smaller images or rebuild them as formatted text.
When is a fixed layout the right call?
Fixed-layout e-books lock every element in place. Font size cannot change, and images stay exactly where the designer put them. That is the format's point — and its limitation.
It exists for page-like, image-heavy design: children's books, comics, cookbooks, highly visual work. The trade-off is that readers cannot adjust text size, and content can get hard to read on small screens. Pressbooks' own assessment is blunt: fixed layout looks good on tablets and poorly on phones, and unless you are doing a genuinely highly specified design, reflowable is the better choice because it works on all devices, not just some.
So the decision rule is simple. If the visual design is the book — a picture book, a graphic novel — fixed layout earns its costs. If the words are the book, reflowable wins.
How should authors test before publishing?
Testing across devices is essential, and it does not require owning a shelf of hardware. Use the preview tools your distribution platform provides to see how the file renders at different screen sizes and settings before you publish. Check three things at minimum: the table of contents navigates correctly, chapter headings hold their hierarchy at the largest font size, and images sit where they should on a phone-width screen.
What this means in practice: format for structure, accept that appearance belongs to the reader, and spend your remaining effort on the failure points — fonts, relative spacing, image sizing. A book that adapts gracefully on a phone will look fine everywhere else. A book built for one perfect page will look broken on most of them.
One honest gap: none of the sources here establishes how any specific store or device handles a given file today, and platform behaviour shifts with firmware updates. Verify against the current documentation of the platforms you publish to rather than treating any single guide as permanent truth.