Today, the only way to load third party ebooks onto a newly purchased Kindle or Kindle App is to use the “Send-to-Kindle” service which accepts EPUB3 files and loads them into your Kindle Library. We know that MOBI files are being used less and less, but we want to continue to support our readers who still use their old Kindles! So we’d love to hear from you about whether you still use MOBI files. Here’s a 2-question survey form you can use to tell us your opinion:

forms.gle/nU4cREmuxdHAHEQc6

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Google DocsDo you use the “older Kindles” link at Project Gutenberg?MOBI (Mobipocket, labeled as “older Kindles” on our download pages) was introduced in 2007. A couple of years later, Amazon launched an advanced version of MOBI and called it KF8 or AZW3 (it’s the download file we label as “Kindle”). We want to know if we should continue making the older version.

Replying to @gutenberg_org@mastodon.social

@gutenberg_org
No, use USB transfer and a free program like Calibre to make azw3/KF8 from epub2 or epub3! The azw3/KF8 is is closer formatting to epub than kfx.

Only K1, K2, and DX family need use actual mobi files, which Calibre can also make.

Send to Kindle uses the Internet twice, gives Amazon a copy, is limited in file size and poorer quality than Calibre conversions. It's Amazon surveillance.

I've converted Gutenberg files for over a decade with free Calibre. Mac, Windows & Linux.

Jul 5, 2026, 17:29 UTCen