An eBook is a digital publication designed for reading on phones, tablets, computers, and dedicated eReaders. For most novels and text-led nonfiction, the most portable production strategy is one clean, validated, accessible EPUB 3 master—not separate EPUB and MOBI files created by default.
That master can be uploaded directly to platforms that accept EPUB and used to generate a Kindle-specific file only when a KDP workflow benefits from KPF. Apple Books, Google Play Books, Kobo, Barnes & Noble Press, libraries, and aggregators may apply their own ingestion rules, metadata fields, cover specifications, and link policies.
“Format once for all platforms” therefore means building one structurally sound source, then creating the smallest number of controlled variants needed for real channel differences. It does not mean uploading an untested file everywhere and assuming every store will render it identically.
These are decision rules, not permanent upload guarantees. Review the linked official requirements immediately before release.
|
Store or channel |
Preferred master or upload | Create a variant when |
Final verification |
| Amazon KDP | EPUB, KPF, or clean DOC/DOCX | KPF or fixed layout serves a documented Kindle need | Kindle Previewer plus KDP online preview |
| Apple Books | Standards-compliant EPUB 3 | Apple-specific features or compliant store links require it | Apple Books Asset Guide and Apple testing workflow |
| Google Play Books | EPUB 3.3 preferred; EPUB 3/2 accepted | A separately offered PDF is intentional | Partner Center processing, preview, cover, and sample |
| Kobo Writing Life | Validated EPUB; supported source conversion is available | Kobo-specific end matter or conversion is needed | Kobo validation guidance, app/device preview, and store sample |
| Barnes & Noble Press | EPUB that meets the current Press guide | Store-specific links or a platform profile requires it | Current upload guide, preview, and live NOOK sample |
| Aggregator | Validated EPUB or supported clean source | The service converts or needs store-specific packages | Aggregator dashboard plus downstream retailer pages |
| Direct sale or ARC | EPUB with clear delivery instructions | A legacy reader audience genuinely needs another file | Download, sideload, reading order, links, and device support |
Formatting follows the distribution model. If the Kindle eBook is enrolled in KDP Select, Amazon requires digital exclusivity under the current program terms; the eBook cannot simultaneously be sold through other digital stores or the author’s site during the enrollment period. Print editions are handled separately.
If the strategy is wide distribution, decide whether to upload directly to each retailer, use an aggregator, or combine the two. A common hybrid is direct KDP plus an aggregator for non-Amazon stores, but fees, account requirements, territorial reach, promotional tools, and update timing should drive the choice.
Do not prepare store-specific files before the channel map is approved. The list of actual retailers determines whether neutral end matter is enough or whether separate store variants are useful.
Create one row for every retailer or distributor and record the current requirements before production begins.
Date every requirement and save the source URL. Platform policies change; an undated checklist becomes a source of errors.
Use reflowable layout for novels, memoirs, essays, and most text-led nonfiction. Readers can resize text, change fonts and themes, rotate the device, and use assistive technology. Exact page coordinates are not stable.
Use fixed layout only when the page design is essential to meaning, such as a picture book, comic, or image-led textbook. Fixed-layout files require separate platform review because support and accessibility behavior vary more sharply.
Start with final edited content. Remove tracked changes, comments, headers, footers, print page numbers, blank verso pages, manual tabs, repeated spaces, and paragraphs used only as vertical spacing.
Use source styles for title, part, chapter, section, body, quotation, list, caption, note, and scene break. A chapter title should be a real heading, not merely large bold text.
Semantic structure supports navigation, consistent styling, conversion tools, search, and assistive technology. It also makes platform-specific styling changes safer because presentation can change without rewriting the reading order.
Create a valid EPUB navigation document and, when appropriate, a visible linked contents page. Use labels that match the chapter headings and remove typed print page numbers.
Do not rely on a retailer to infer the table of contents from visual styling. Generate it from structure and test the exported links.
Keep body typography flexible. Readers should be able to enlarge text without overlap, clipping, or horizontal scrolling.
Use high-quality source images, resize them according to the strictest target channel, and keep the file package efficient. Place images in reading order and use responsive presentation rather than Word text wrapping.
Add meaningful alternative text to informative images and mark decorative images appropriately. For charts, maps, or complex diagrams, include enough nearby explanation or a long description to convey the same information.
Set publication language, use logical headings, write descriptive link text, maintain adequate contrast, and test enlarged text. Accessibility is not a final patch; it is a requirement that influences the source, navigation, images, tables, and CSS.
W3C’s EPUB 3.3 Recommendation defines the current EPUB distribution and interchange format. A professional master contains structured XHTML, CSS, navigation, metadata, and packaged resources in a valid container.
Export the EPUB from a tool suited to the book and operating system, or use a professional formatter. Inspect the result rather than trusting the export button. A tool can generate valid files while still preserving poor source structure or inaccessible design decisions.
Run EPUBCheck and resolve structural errors. Review warnings, missing resources, invalid markup, metadata problems, and navigation issues before distribution.
Run Ace to identify accessibility problems, then complete manual checks for reading order, heading logic, alternative text quality, links, color, and usability.
Open the file in at least one independent EPUB reading system, test a phone-size view, and use Kindle Previewer for Amazon rendering. Change font size, orientation, and theme; open every contents entry; inspect notes, images, tables, lists, and scene breaks.
KDP accepts EPUB and also supports KPF created with Kindle Create. Use KPF when Kindle-specific themes or fixed-layout workflows justify it. Do not create MOBI by default; KDP says fixed-layout MOBI uploads stopped being accepted in March 2025.
A retailer may reject or de-emphasize files that aggressively direct readers to a competing store. Keep the master’s end matter neutral, or create controlled variants whose store links match the destination. Ensure the content, edition, and identifier remain correct.
Create PDF only when it is a deliberate, separately distributed fixed-page product. Do not substitute a print PDF for the EPUB master. A PDF and EPUB sold separately may require distinct product metadata and identifiers.
A fixed-layout title may need channel-specific packaging or testing. Treat each output as a controlled build from the same approved source, not a casual conversion from the last retailer’s file.
These examples remove common causes of rejection, inconsistency, and reader frustration.
|
Cross-platform problem |
Before | After |
Result |
| Default file plan | EPUB plus MOBI for every store | Validated EPUB 3 master; KPF only when needed | Fewer obsolete and duplicate files |
| Chapter structure | Large bold text and blank lines | Semantic headings and structural chapter breaks | Consistent navigation and conversion |
| Body typography | Hardcoded font, size, width, and color | Reader-controlled type with relative CSS | Usable across devices and themes |
| End matter | Amazon-only links in every file | Neutral master or destination-specific variant | Lower policy risk and better reader path |
| Table of contents | Typed page numbers | EPUB navigation with live targets | Works in reflowable reading systems |
| Images | Floating Word images and untested sizes | Responsive images, captions, alt text, optimized assets | Stable reading order and accessibility |
| Metadata | Different title or author spelling by store | One dated release metadata sheet | Cleaner edition identity across channels |
| Release QA | Check the source once | Validate master, inspect conversions, audit live samples | Catches platform-specific failures |
The file is only half the product. Use a release metadata sheet so every platform receives the same title, subtitle, contributor spelling, series name, edition, language, publisher, description, publication date, and identifier.
Categories and keywords differ by store, so translate the same positioning into each platform’s current fields rather than copying invalid category codes. Do not keyword-stuff the title or contributor fields.
If the eBook uses an ISBN, assign a digital ISBN rather than reusing the paperback or hardcover number. Amazon KDP does not require an ISBN for an eBook and supplies an ASIN, but other distributors may require or accept an ISBN.
Some platforms ingest the EPUB directly; others convert a source file or generate an internal package. Use the platform’s online preview and download the converted file when the workflow allows it.
After publication, inspect the live product page and sample on every store. Search by title, author, series, and identifier. Confirm the product format is labeled correctly and that the sample begins where intended.
Track platform-specific URLs in the release sheet, update the author website and campaigns, and monitor support dashboards for ingestion warnings. Archive the master, variants, validation reports, source file, cover, metadata sheet, and release date so updates can be rebuilt cleanly.
KDP’s current supported-formats page recommends commonly used workflows including DOC/DOCX, KPF, and EPUB. It also lists HTML ZIP, RTF, TXT, and limited-language PDF cases. Use Kindle Previewer before upload and the KDP online preview after conversion.
Use a standards-compliant EPUB and follow the current Apple Books Asset Guide for content, cover, metadata, and delivery rules. Test the file in Apple’s supported workflow and avoid assuming that a Kindle-specific KPF can be reused.
Google Play Books currently accepts EPUB 3.3, EPUB 3, and EPUB 2, with EPUB 3.3 preferred. Its help center also documents PDF uploads. Decide whether the PDF is a genuine product option rather than uploading it as an automatic substitute for a reflowable edition.
Kobo’s current help center emphasizes validated EPUB files and documents upload/conversion routes for supported source formats. It also states that reflowable EPUBs should not contain preset page numbers or running headers and footers. Test the Kobo result rather than relying only on the source preview.
Aggregators can reduce account and upload work, but acceptance, conversion, fees, store coverage, and update timing vary. Prefer sending a validated EPUB when the service accepts one and review the downstream files or store samples after distribution.
EPUB is the most interoperable direct-delivery format for current reading systems. A service may also generate legacy or platform-specific ARC files. Give readers clear sideloading instructions and do not confuse an ARC delivery format with the retailer upload master.
Choose a tool by operating system, book complexity, outputs, accessibility, and how easily a correction can be regenerated—not by the number of decorative templates.
|
Tool or route |
Runs on | Best for |
Main limitation or check |
| Vellum | Mac | Platform-specific EPUBs and print from one project | Mac only; verify styling and store variants |
| Atticus | Browser-based workflow | Cross-platform prose formatting and print/eBook output | Confirm current export and accessibility behavior |
| Kindle Create | Mac and Windows | KDP-specific KPF and Kindle preview workflow | Not a complete wide EPUB pipeline |
| Reedsy Book Editor | Browser-based workflow | Simple text-led books and low-cost production | Fewer advanced layout controls |
| Calibre | Desktop platforms | EPUB inspection, editing, and controlled conversion | Not a substitute for cleaning a damaged source |
| Professional service | Any author operating system | Complex, fixed-layout, accessibility-sensitive, or deadline work | Require final files, validation reports, proof, and revision terms |
Vellum’s current site says it is Mac-only and generates validated EPUB 3/EPUB 2 output, image optimization, platform-specific eBooks, and Ace-approved accessible output. That makes it strong for Mac-based prose workflows.
Kindle Create is useful for KDP-specific KPF output but is not a complete wide-distribution pipeline by itself. Tools such as Atticus, Reedsy, and Calibre can serve different roles; verify current output, licensing, and accessibility before adopting one.
Different reading systems apply different defaults and feature support. Simplify CSS, avoid pixel-perfect expectations, compare the same font-size conditions, and correct only differences that damage hierarchy, meaning, or usability.
EPUBCheck tests the standard; a retailer can impose additional profile rules. Read the platform’s ingestion message, compare it with current help documentation, make a minimal source change, rebuild, and validate again.
Check the EPUB navigation document, unique anchors, label hierarchy, and exported package. Do not rely on a retailer-generated contents list when the master lacks valid navigation.
Confirm whether the cover is embedded in the EPUB and separately supplied according to Google’s current file guidelines. Use consistent filenames and metadata, remove obsolete uploads, and allow the updated file to finish processing.
Remove running print furniture from the reflowable source. Page numbers and headers are not stable in reflow and Kobo’s guidance specifically warns against preset versions.
Use neutral end matter in the master or a channel-appropriate variant. Remove competing-store purchase links from that retailer’s file and keep author-site links compliant with the platform’s policy.
Use Unicode text, valid XHTML, declared language, and properly embedded fonts only when licensing and platform support allow. Replace unsupported glyph hacks and retest on more than one reader.
Compare the EPUB package metadata, copyright page, distributor feed, and platform setup against the release metadata sheet. Correct the source of truth first, then update each channel.
A valid, reflowable EPUB 3 is the best wide-distribution master for most prose books. Retailers may still apply their own ingestion, cover, metadata, and content rules.
No. Do not create MOBI by default. Use EPUB as the master and create KPF or another platform-specific file only when a documented workflow requires it.
Often, yes for a clean reflowable title, but validate the file and check each store’s current profile. Retailer-specific links, fixed layout, cover handling, or platform features may justify variants.
Yes. Google’s current help page says it accepts EPUB 3.3, EPUB 3, and EPUB 2 and prefers EPUB 3.3.
Kobo documents conversion routes for DOC/DOCX and other supported inputs, but a validated EPUB gives the publisher more control over the delivered structure. Review Kobo’s current File Types & Sizes page before upload.
No. KPF is a Kindle package used with KDP. It is not the general wide-distribution format for Apple Books, Google Play, Kobo, or other EPUB channels.
No. If the digital edition uses an ISBN, assign one to the eBook product. KDP can publish an eBook without an ISBN and assigns an ASIN.
Maintain one release metadata sheet as the source of truth, then map it into each platform’s fields. Record any platform-specific category or description changes without altering the core identity.
Direct publishing offers channel control; an aggregator reduces administrative work. Compare fees, store reach, promotional access, update timing, support, and file ownership. Many publishers use a hybrid.
The best all-platform workflow is not EPUB plus MOBI plus a stack of one-off conversions. It is one clean semantic source, one validated and accessible EPUB 3 master, and only the controlled variants required by a real platform difference.
Map the stores, build the master, validate it, test it across reading systems, upload consistent metadata, inspect every converted result, and audit the live product pages. That process minimizes rework while protecting the reader experience in every channel.
