MOBI Format Guide

Available Conversions

About MOBI Format

MOBI (Mobipocket) is a proprietary e-book format originally developed by Mobipocket SA, a French company founded in 2000. Amazon acquired Mobipocket in 2005 and used the MOBI format as the foundation for Kindle e-books. The format was the primary format for Amazon Kindle devices until being superseded by the more advanced AZW3 (KF8) format. In 2022, Amazon announced they would no longer accept MOBI files for Kindle publishing, signaling the format's transition to legacy status.

History of MOBI

The Mobipocket format was created in 2000 to provide e-books for PDAs (Personal Digital Assistants) and early smartphones. It was based on the Open eBook Publication Structure (OEBPS) with Palm Database (PDB) container format. When Amazon acquired Mobipocket in 2005, they adapted the format for the first Kindle released in 2007. The MOBI format dominated the Kindle ecosystem for years, with files using .mobi, .prc, or .azw extensions. Amazon developed AZW3 (Kindle Format 8) in 2011, which added HTML5 and CSS3 support. By 2022, MOBI was officially deprecated for Kindle Direct Publishing in favor of EPUB source files.

Technical Structure

MOBI files use the Palm Database (PDB) container format with PalmDOC or HUFF/CDIC compression for text content. The format supports basic HTML markup, limited CSS styling, images (JPEG and GIF), and a table of contents. Unlike EPUB, MOBI is a binary format that's not human-readable without special tools. The format includes DRM support through Amazon's proprietary scheme. MOBI files can contain both MOBI and KF8 (AZW3) content simultaneously, with older Kindles reading the MOBI portion and newer devices reading the KF8 portion. The format has limitations compared to modern standards: no support for audio/video, limited CSS, no JavaScript, and basic typography options.

Common Applications

MOBI was historically the primary format for Amazon Kindle devices and apps. It remains compatible with older Kindle e-readers (Kindle 1, 2, 3, DX, Keyboard, Touch) and Kindle apps on various platforms. The format is still used by some third-party e-book stores and libraries. Calibre, the popular e-book management software, can read, create, and convert MOBI files. Many legacy e-book collections contain MOBI files that users may want to convert to more modern formats like EPUB or AZW3. The format is also found in DRM-free e-book bundles from sites like Humble Bundle and StoryBundle.

Advantages and Disadvantages

Why Convert MOBI Files?

• Universal Compatibility: Convert to EPUB for non-Kindle e-readers (Kobo, Nook, etc.)
• Modern Kindle Format: Upgrade to AZW3 for better formatting on newer Kindles
• Print and Share: Convert to PDF for printing and universal viewing
• Edit Content: Convert to DOCX or ODT for editing in word processors
• Web Publishing: Convert to HTML for blogs and websites
• Future-Proofing: Migrate from deprecated format to open standards
• Documentation: Convert to Markdown or AsciiDoc for technical docs
• Russian E-readers: Convert to FB2 for PocketBook and CIS devices
• Data Extraction: Convert to JSON, XML, or CSV for cataloging
• Text Analysis: Convert to TXT for NLP and text processing

Software That Opens MOBI Files