What Is EPUB Builder?
EPUB Builder creates properly structured EPUB ebook files from your text content. Add chapters, set metadata (title, author, language, cover image), and the tool packages everything into a valid EPUB 3 file that works on Kindle, Apple Books, Kobo, and other e-readers.
How to Use This Tool
Enter your book’s metadata (title, author, description), upload a cover image, then add chapters with their content using the rich text editor or by pasting Markdown. Arrange chapter order, then export the complete EPUB file. The entire build process runs in your browser — your manuscript is never uploaded to a server.
Why Use EPUB Builder?
EPUB is a structured zip format with specific XML requirements that are tedious to assemble manually. Dedicated ebook software like Calibre has a steep learning curve. This tool handles the EPUB structure automatically and gives you a standards-compliant file in minutes — free, private, and with no publishing platform lock-in. For a detailed walkthrough, see our step-by-step guide.
Frequently Asked Questions
What is EPUB and why would I use it instead of PDF?+
EPUB (Electronic Publication) is the standard ebook format used by Apple Books, Google Play Books, Kobo, Barnes & Noble Nook, and every mainstream ebook reader except Amazon Kindle. Unlike PDF, EPUB reflows text to fit any screen size — phones, tablets, e-ink readers — and lets users change font, font size, and theme. For books meant to be read as books, EPUB is strictly better than PDF.
Does EPUB work on Kindle?+
Yes, as of late 2022 Amazon accepts EPUB directly. You can email an EPUB file to your kindle.com address, upload it to your Kindle library via the Send to Kindle web interface, or sideload it to a Kindle device via USB. Amazon converts it to their internal format automatically. For Kindle Direct Publishing (KDP) you can upload EPUB files as the source format.
Is the EPUB I create here valid? Will it pass EPUBCheck?+
Yes. Our tool generates EPUB 3 files following the OCF (Open Container Format) specification — proper mimetype file (uncompressed, first in zip), META-INF/container.xml, OPF package document with Dublin Core metadata, navigation document (toc.xhtml), and XHTML5 chapter files. The output passes EPUBCheck, the reference validator used by Apple Books and other strict distributors.
Can I import a Markdown file or Word document as my source?+
Markdown pasting is supported — paste your full Markdown into the chapter content field and we'll convert headers, emphasis, lists, links, and code blocks to proper HTML on export. For Word documents, export to HTML from Word first (File → Save As → Web Page, Filtered), then paste the body. For large multi-chapter imports, use the 'Auto-split on heading' feature which turns each H1 in pasted content into a new chapter.
How do I add images to my ebook?+
Paste images inline as base64 data URIs in your chapter HTML, or reference them via img tags. Our export bundles any base64-encoded images automatically. Keep total image weight under 10 MB for best compatibility with older readers and email attachment limits. For a cover image, use the dedicated Cover upload — it gets special treatment in the EPUB metadata so readers display it properly.
Why is there no ISBN field? Do I need one?+
Our tool generates a UUID identifier for every ebook, which EPUB requires. If you have a real ISBN (needed for commercial retail distribution through most bookstores), you can edit the identifier field to use it in urn:isbn format. For personal use, free distribution, or publishing only through Amazon KDP, a UUID is fine and Amazon assigns its own ASIN anyway.
Which ebook readers does the EPUB output support?+
EPUB 3.0 output works on every major reader: Kindle (after conversion to KFX via Send to Kindle or Calibre), Apple Books, Kobo, Google Play Books, Adobe Digital Editions, and any web-based reader. The generator validates against EPUB 3.0 spec before download, so the output passes most store ingestion checks. KDP requires a Kindle Format conversion step after EPUB export; the generator does not produce KFX directly because Amazon controls that format.
Can I include images and custom fonts in the EPUB?+
Yes. Images are embedded directly into the EPUB ZIP and referenced from the chapter HTML. Custom fonts can be embedded as well, though some readers (notably older Kindle hardware) limit font embedding for licensing reasons. The generator warns if your fonts are missing the licensing metadata that ebook readers check before honoring an embedded font.
Built by Derek Giordano · Part of Ultimate Design Tools
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