Technical Format Comparison Verified Engineering Specs

EPUB vs MOBI: Open E-Book Standard vs Kindle Legacy Format

Technical comparison between the international IDPF EPUB open format and Amazon's legacy MOBI e-book format.

The Executive Verdict

Choose EPUB for all modern e-books, Apple Books, Kobo, and Amazon Kindle (via Send to Kindle). MOBI is a discontinued legacy format and should only be used on vintage 1st/2nd generation Kindle hardware.

Convert EPUB to MOBI for Kindle

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Technical Specification Matrix

Direct architectural comparison between EPUB and MOBI

Feature / Metric	EPUB Specification	MOBI Specification
Standard Governance	W3C / IDPF Open International Standard	Proprietary Amazon / Mobipocket (Discontinued)
Amazon Kindle Status (2026)	Official format supported by Send to Kindle	Deprecated; no longer supported on modern Send to Kindle
Typography & Layout Engine	Modern HTML5, CSS3, reflowable & fixed-layout	Primitive HTML 3.2 styling; limited CSS support
Custom Font Embedding	Full OTF, TTF, and WOFF font embedding	Very limited custom font rendering
Cross-Platform Compatibility	Apple Books, Kobo, Nook, Google Play Books, Android, PC	Kindle hardware and Kindle reading apps only
Interactive Elements & Audio	EPUB 3 supports embedded audio, video, and math	Text and low-resolution static images only

Decision Matrix: Which Format Should You Use?

Recommended format choices by practical real-world scenario

Publishing E-Books for Amazon Kindle Use EPUB

Amazon officially deprecated MOBI; Send to Kindle now mandates EPUB files for enhanced typesetting and Bookerly fonts.

Reading on Kobo, Nook, or Apple Books Use EPUB

Natively opens on all major non-Amazon e-readers without requiring conversion software.

Vintage 1st Generation Kindle Devices (2007-2011) Use MOBI

Legacy Kindle hardware without Wi-Fi or modern firmware requires sideloading MOBI files over USB.

Complex Math, Textbooks & Poetry Use EPUB (v3)

Full MathML and CSS flexbox formatting ensures formulas and indents render correctly across screen sizes.

Frequently Asked Questions

Expert answers to common EPUB vs MOBI questions

Does Amazon Kindle still support MOBI files?

No. Amazon discontinued MOBI support for 'Send to Kindle' in 2022. Amazon now officially requires EPUB format, which Kindle automatically converts to its modern AZW3 / KFX rendering engine.

Can I convert an EPUB e-book to MOBI or PDF?

Yes. OpenFileConverter converts EPUB e-books to Kindle MOBI and print-ready PDF with custom typesetting, margin control, and font embedding locally in your browser with zero server uploads.

What is the difference between EPUB 2 and EPUB 3?

EPUB 2 is based on XHTML 1.1 and simple CSS. EPUB 3 is based on HTML5 and CSS3, supporting embedded audio/video narration, accessible MathML equations, responsive media queries, and vertical writing modes for Asian typography.

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