EPUB vs MOBI: eBook Formats Compared
Published on March 27, 2026
EPUB is the universal eBook format that works on Apple Books, Kobo, Google Play Books, Nook, and most reading apps. MOBI was Amazon's Kindle format, but Amazon stopped accepting MOBI uploads in 2023 and now prefers EPUB. For almost every use case today, EPUB is the right choice.
Format Structure
Both EPUB and MOBI are reflowable formats, meaning text adjusts to fit any screen size. EPUB is based on HTML, CSS, and XML packaged in a ZIP container. MOBI uses a proprietary binary format that Amazon acquired from Mobipocket in 2005. EPUB 3 supports embedded audio, video, and interactive content. MOBI has no support for multimedia. Unlike PDF, which uses fixed layouts, both formats adapt to different screen sizes and font preferences.
Device and App Compatibility
EPUB works on nearly every eReader and reading app except older Kindle devices. Apple Books, Kobo, Google Play Books, Calibre, and most third-party apps support EPUB natively. MOBI only works on Amazon Kindle devices and the Kindle app. Since 2022, Amazon converts uploaded EPUBs to its internal KF8/AZW3 format automatically. You can send EPUB files directly to your Kindle via email, and Amazon handles the conversion.
File Size and Features
EPUB files are typically 10-30% smaller than MOBI files for the same book because EPUB uses more efficient compression. EPUB supports proper table of contents, metadata tags, font embedding, and MathML for equations. MOBI metadata support is limited, and complex formatting often breaks. For publishers distributing through multiple platforms, EPUB is the single source format that works everywhere.
DRM and Distribution
EPUB uses Adobe DRM or Apple FairPlay for copy protection. MOBI uses Amazon's proprietary DRM. If you buy a DRM-protected MOBI book from Amazon, it only works within the Kindle ecosystem. DRM-free EPUB files can be read on any compatible device. For self-published authors, Amazon's KDP now accepts EPUB uploads and converts them internally, so there is no reason to create MOBI files manually.
Which Format Should You Use?
Use EPUB. It is the industry standard, works on the widest range of devices, supports modern features, and even Amazon accepts it now. MOBI is effectively a dead format. If you have old MOBI files, tools like Calibre can convert them to EPUB. For documents that need a fixed layout instead of reflowable text, consider PDF vs DOCX to pick the right format.
Need to convert documents between formats? Use our Word to PDF converter or HTML to PDF tool. For more format comparisons, see ODT vs DOCX and RTF vs DOCX.