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The missing Kindle toolkit. Dictionaries, books, comics. Single Rust binary. ~7,000x faster than kindlegen for Modern Greek, ~40x faster for French.

30 starsRust

Kindling – reverse-engineered kindlegen, ~7,000x faster in Rust

by ciscoriordan·Apr 7, 2026·2 points·1 comment
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AI Analysis

●●●BangerWizardryDark HorseZero to One

Reverse-engineered undocumented MOBI format — builds dictionaries in 6 seconds vs 12 hours.

Strengths
  • •Byte-by-byte reverse engineering of undocumented Amazon format is genuine technical craft.
  • •7000x speedup (12 hours to 6 seconds) solves a real pain point for dictionary publishers.
  • •Single static binary with no runtime dependencies works across Mac, Linux, Windows.
Weaknesses
  • •Very narrow audience — only matters if you're building Kindle dictionaries specifically.
  • •Amazon pushing EPUB means MOBI dictionary format may become increasingly obsolete.
Category
Open Source
Target Audience

Dictionary publishers, Kindle content creators, ebook tooling developers

Similar To

kindlegen · Kindle Previewer · Ebook-convert

Post Description

Amazon has been slowly killing kindlegen since 2020. First they dropped the Linux binary, then stopped distributing the standalone CLI entirely. The only copy left is hidden inside Kindle Previewer 3. Most people building Kindle dictionaries have been getting by with unsupported copies from older installations.

Amazon has moved a lot to EPUB. But sideloaded dictionaries still require MOBI. There's no alternative format for custom Kindle dictionaries.

The MOBI dictionary format is barely documented by Amazon, and the MobileRead wiki has partial community documentation, but a lot of the dictionary-specific format had to be reverse-engineered from kindlegen's output byte by byte.

I was building a Greek dictionary with 80K headwords and 452K inflected forms, and kindlegen couldn't handle it - 12+ hours on a Mac under Rosetta, frequently running out of memory and crashing before finishing. Kindling builds the same dictionary in 6 seconds.

Binaries for Mac, Linux, Windows: https://github.com/ciscoriordan/kindling

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