Question 1

What does this tool do?

Accepted Answer

It extracts text from your PDF using a pure-JS PDF parser, then generates a MOBI ebook file with a valid PalmDB header, PalmDOC header, MOBI header, optional EXTH metadata, and a series of text records (max 4096 bytes each). The result can be sideloaded to a Kindle device or opened in the Kindle app.

Question 2

How does the MOBI structure work?

Accepted Answer

A MOBI file starts with a PalmDB header (78 bytes) containing the book name, type ('BOOK'), creator ('MOBI'), and a record count. Then comes a record info table (8 bytes per record) listing each record's offset and unique ID. Record 0 contains the PalmDOC header (compression, text length, record count, record size, encryption), the MOBI header (identifier 'MOBI', text encoding, file version), and optional EXTH metadata (title, author, language). Records 1..N are the text records — chunks of HTML/text up to 4096 bytes each.

Question 3

Is this a full MOBI implementation?

Accepted Answer

No — it's a simplified subset. We generate uncompressed (compression=1=none) text records containing HTML-formatted paragraphs. We do NOT implement: PalmDOC RLE compression, HuffCDic compression, DRM, embedded fonts, images, KF8 (AZW3) layer, dictionaries, periodicals, or TOC via guide. The output is readable on most Kindle devices and apps but may not pass strict validators. For full-featured MOBI generation, use Calibre's ebook-convert.

Question 4

What extra features does this tool have compared to others?

Accepted Answer

10 extras: (1) Drag-drop input. (2) Page range selector. (3) Custom title and author metadata. (4) Three chapter modes (page / heading / single — same as our EPUB converter). (5) Configurable text encoding (CP1252 / UTF-8). (6) Stats — record count, word count, character count. (7) Chapter detection (splits at headings, generates

tags). (8) Bookmark support (generates between chapters). (9) Conversion history in localStorage (last 10). (10) Shareable URL with conversion options.

Question 5

Is my PDF uploaded anywhere?

Accepted Answer

No. All PDF parsing and MOBI generation happens in your browser. File contents never leave your device.

Question 6

Why use MOBI instead of AZW3 / KF8?

Accepted Answer

MOBI is the older Mobipocket format — supported by every Kindle ever made. AZW3 (KF8) is the newer format with better formatting support (CSS, fonts, drop caps). Old Kindles (pre-2012) only read MOBI. Newer Kindles read both. Use MOBI for maximum compatibility, AZW3 for modern features.

PDF to MOBI Converter

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