Get in Touch

What eBook Formatting Actually Covers

eBook formatting means building a reflowable EPUB3 file that renders correctly across Kindle, Kobo, Apple Books, Google Play, and Nook. The text reflows to fit any screen width, font size, or reading mode the reader selects. Page breaks are not fixed. Line lengths shift. Images scale. The formatter’s job is to make sure the manuscript still looks deliberate after the reader engine takes over layout decisions.

This is not the same as print formatting, which produces a fixed-page PDF where every line break and page number is locked. It is also not “format conversion” — running a Word file through a converter and shipping whatever comes out. Real ebook formatting involves semantic markup decisions, CSS scoped to each retailer’s reader engine, and accessibility metadata that survives validation at upload.

EPUB3 structure, decoded

• OPF package — the manifest that lists every file in the EPUB and their roles. Missing entries fail validation at KDP and Apple Books.
• NCX + nav doc — two parallel navigation systems. NCX is legacy EPUB2; nav doc is modern EPUB3. Both must agree, because older Kindle devices still read NCX while newer engines read the nav doc.
• Spine — the reading order. Affects page numbering, location syncing across devices, and whether “next chapter” gestures work.
• Stylesheet (CSS) — one or more CSS files referenced by the OPF. Reader engines vary in support, and what works on iBooks may strip on Kobo without warning.
• Content documents — XHTML files, one per chapter or section, validated against the EPUB3 schema before any retailer accepts upload.

CSS limits: what reader engines actually support

Apple Books supports the broadest CSS subset, including most CSS3 features and transforms with caveats. Kobo strips most layout CSS, keeping typography and color but discarding floats, flex, and absolute positioning. Kindle (KFX) honors typography and limited layout, ignores transforms, and silently drops animations and most @media queries. Google Play Books is strict on CSS validation but otherwise broad in support. Universal-safe properties that render the same everywhere: font-family, font-size, line-height, margin, text-indent, color, font-style, font-weight, and text-align. Anything beyond that needs per-retailer testing on actual devices, not just emulators. Images must be RGB at 96 to 300 DPI in JPEG or PNG — WebP is rejected by most engines.

Accessibility and semantic markup

EPUB3 accessibility metadata is required by some retailers, and from June 2025 the EU Accessibility Act mandates it for any ebook sold into the European Union. Required fields include schema:accessibilityFeature (alternativeText, structuralNavigation), schema:accessMode, and schema:accessModeSufficient. Markup rules follow: every <img> needs an alt attribute, headings must be hierarchical with no skipped levels (no h1 followed by h3), tables need scope attributes on th cells, and the document language must be declared on the html root. Trade publishers reject files that fail these checks at ingestion.

Why Authors Choose Professional eBook Formatting

• Cross-retailer consistency — one source EPUB3 that passes validation at Amazon, Apple, Kobo, Google Play, and Nook without per-store rebuilds.
• Accessibility compliance — metadata and markup that meet EU Accessibility Act 2025 requirements, so the book stays sellable in European markets.
• Working navigation — both NCX and nav doc generated and synchronized, so chapter jumps work on legacy Kindles and modern engines alike.
• Image and font handling — RGB conversion, DPI normalization, embedded font licensing checks, and fallback stacks for engines that strip custom fonts.
• Validation before upload — EPUBCheck and Ace by DAISY run on the final file, so retailer ingestion does not bounce the submission back.

The output format determines the workflow. Image-heavy titles need fixed-layout EPUB; KDP-bound files clear validation with the KDP upload step. Beyond KDP, Apple Books, Kobo, and Draft2Digital each have store-specific quirks worth handling at the formatting stage rather than after upload.

Frequently Asked Questions About eBook Formatting

Do you deliver EPUB3 or also a Kindle-specific file?
The deliverable is a validated EPUB3. Amazon converts EPUB3 to KFX during upload, so a separate MOBI is no longer needed and KDP no longer accepts it as the preferred format.

Will the file pass EPUBCheck without warnings?
Yes. Every file is run through EPUBCheck and accessibility validation through Ace by DAISY before delivery, and any flagged issues are resolved before the file leaves the studio.

Can I include custom fonts in the ebook?
Custom fonts can be embedded when the license permits ebook embedding. Apple Books and Google Play render them reliably; Kindle and Kobo may substitute the reader’s default font on some devices, so a fallback stack is always declared.

How are images handled inside the EPUB?
Images are converted to RGB, normalized to 96 to 300 DPI, saved as JPEG or PNG, and given alt text. WebP and CMYK are rejected by reader engines and are converted before packaging.

Does the formatting include accessibility metadata for the EU Accessibility Act?
Yes. The OPF includes schema:accessibilityFeature, schema:accessMode, and schema:accessModeSufficient, and the markup follows hierarchical headings, alt text, and language declaration rules required from June 2025 onward.