ebook-convert from Calibre. Basic usage:
ebook-convert input.epub output.mobi
Output format is inferred from the output file extension. Supported: mobi, azw3, epub, pdf, txt, docx, fb2, and more.
Format choice matters
- mobi legacy; Amazon stopped accepting it for Send-to-Kindle in 2022, new Kindles don't read it. Only when explicitly requested.
- azw3 modern Kindle format, keeps formatting/CSS best. Prefer for Kindle devices.
- epub universal; Kindle (2022+) and Send-to-Kindle accept it directly, no conversion needed.
Useful options
# cover for mobi (mobi doesn't embed covers well without this)
ebook-convert in.epub out.mobi --mobi-file-type=both
# nicer azw3 with metadata cover
ebook-convert in.epub out.azw3
# fix TOC during conversion
ebook-convert in.epub out.azw3 --toc-threshold=50
Workflow
- Locate the input file (find if path not given).
- Run
ebook-convert <in> <out>; conversion can take 10-60s, use a generous timeout. - Verify the output file exists and has non-zero size.