How to Translate a MOBI or AZW3 Ebook (and Read It on Kindle)

You can translate a MOBI or AZW3 ebook as a whole file, as long as it is DRM-free. Before you upload it, make one decision: where will you read the translation? If the answer is a Kindle over USB, upload the MOBI or AZW3 file as it is. If you want to use Send to Kindle, read on Kobo or Apple Books, or publish the translation, convert the book to EPUB first and translate the EPUB. Amazon's Send to Kindle service does not take MOBI files, and Amazon's publishing service no longer accepts them either.

Most failed attempts happen before any translation starts. A file bought in the Kindle store is usually locked to your account, and renaming or converting it does not unlock it. We wrote a free header checker that tells you in a second whether a file is protected, which generation of the Kindle format it is, and what language it declares. It reads the same encryption field that BookTranslator's MOBI reader checks before it accepts a file.

Quick Answer: Which File Should You Upload?

The rest of this guide explains each row and how to check your file.

Step 1: Check the File Before You Upload It

A MOBI-family file starts with a small header that states, among other things, whether the content is encrypted. You do not need to open the book to read it. Download inspect_kindle_file.py and run it on your file:

python3 inspect_kindle_file.py "My Book.azw3"

It needs only Python 3, and it never changes the file. We tested it on three free downloads of Franz Kafka's Die Verwandlung from Project Gutenberg (eBook #22367), which is in the public domain in the US, and on one copy we altered on purpose:

Both Gutenberg files also declared UTF-8 text and the language tag de. The third file is not a real store purchase. We changed one 2-byte field to show what a protected file looks like to the checker. The README lists the download links, the file hashes, and the exact change, so you can repeat the test.

What the result means:

• Encryption: none. The file can be read. Whether you are allowed to translate it is a separate question. See how to check an ebook for DRM and usage rights.
• Encryption: anything else. BookTranslator's MOBI reader stops at this field and refuses the file, so the task cannot go ahead. Converting the file in another program does not change this, because a converter cannot read encrypted text either.
• "KFX with DRM" or "Topaz book". These are newer or older Amazon store formats, not MOBI. They also need a DRM-free source.

Where DRM-free MOBI and AZW3 files come from

• Public-domain libraries. Project Gutenberg offers both an older Kindle file and a KF8 file for many books, as in the test above.
• The author or publisher. Many send review copies or direct sales as DRM-free MOBI or EPUB. Ask for EPUB if you can; it gives you more options later.
• Your own files. Old manuscripts that you converted with Kindle tools or calibre years ago are usually unprotected.
• Kindle store purchases. Since January 20, 2026, Amazon has let verified buyers download EPUB or PDF for books whose publishers marked them DRM-free, according to KDP's DRM page. If that option appears for your book, download the EPUB instead of trying to use the Kindle file.

Step 2: Decide Whether to Convert to EPUB First

BookTranslator takes .mobi, .azw, and .azw3 uploads directly. Both downloads, the translated file and the bilingual file, keep the extension you uploaded. Behind the scenes, the translated book is rebuilt with calibre's ebook-convert, and calibre's manual says its MOBI output is the older MOBI 6 format by default. That applies to AZW3 uploads too: the download is named .azw3, but the checker will report it as MOBI 6. MOBI 6 is the format with the widest device support, but it has fewer layout options than KF8. If your source book uses KF8-only styling, expect a simpler layout in the translation.

That is fine for reading on a Kindle. It becomes a problem when you want to do anything else with the result:

• Send to Kindle does not take MOBI or AZW3. Amazon's Send to Kindle page lists HTML, RTF, TXT, JPEG, GIF, PNG, BMP, PDF, and EPUB.
• Amazon no longer accepts MOBI for publishing. KDP stopped accepting MOBI for reflowable books on August 1, 2021, and for fixed-layout books on March 18, 2025. It asks for EPUB, DOCX, or KPF instead (KDP MOBI FAQ).
• Most reading apps outside Amazon prefer EPUB. Kobo, Apple Books, and Google Play Books all read EPUB.

So convert first when the translation needs to end up in any of those places. With calibre installed, one command does it:

ebook-convert "My Book.azw3" "My Book.epub"

Then translate the EPUB. You get EPUB files back, and the bilingual EPUB shows each translated paragraph next to the original. Our guide to bilingual EPUB layouts shows what that looks like and how to check it.

Two practical rules for the conversion:

1. Convert from the best file you have. If you have both a MOBI and an AZW3 of the same book, convert the AZW3. The MOBI 6 copy is the simpler one, and a converter cannot add back what it lacks.
2. Check the EPUB before you pay to translate it. Open it in a reader and look at the table of contents, a chapter break, a footnote, and an image. Fix a broken conversion now; a translation will copy the problem into another language.

Step 3: Translate the Whole Book

Upload the file on the EPUB translator page, which also takes MOBI, AZW, and AZW3 files, choose the target language, and check the price shown before you pay. A whole-file upload keeps chapters together, so names and terms stay consistent from one chapter to the next. That is the main thing you lose by pasting chapters into a chat window one at a time.

When the task finishes, the History page offers two downloads:

• Target-only: the book in the new language.
• Bilingual: the original and the translation together, which helps if you are reading in a language you are still learning, or checking a passage you are unsure about.

For a book you plan to publish or share widely, treat the result as a draft and have a fluent reader review it. A human post-editing pass is the usual way to do that.

Step 4: Get the Translation onto a Kindle

The route depends on the file you have.

You translated a MOBI or AZW3 file. Copy the downloads to the Kindle over USB. The specifications for the 2024 Kindle Paperwhite Signature Edition list "unprotected MOBI" and "Kindle Format 8 (AZW3)" as formats it reads natively (Amazon product page). On Windows, the Kindle shows up as a drive; drop the files into its documents folder. On a Mac, Amazon says Kindle models released in 2024 and the Kindle Scribe need its Send to Kindle for Mac app to transfer files over USB (Amazon USB help). Older models mount as a drive on a Mac too.

You translated an EPUB. Use Send to Kindle on the web, in the Kindle app, or by email. Amazon converts the EPUB for your devices. If it fails, our Send to Kindle troubleshooting guide walks through the usual causes.

Whichever way you choose, open the book on the device and check the same four things as before: the table of contents, a chapter break, a footnote, and an image. Our e-reader testing checklist has a longer list if the book matters.

Common Problems

Frequently Asked Questions

Can I translate a Kindle book I bought?

Only if you can get a DRM-free file. Check Manage Your Content and Devices for an EPUB or PDF download option, which Amazon now offers for titles the publisher marked DRM-free. If there is none, ask the publisher or look for an existing licensed translation. Our DRM guide covers the options in detail.

Is AZW3 the same as AZW?

Not quite. AZW3 is Amazon's name for Kindle Format 8 (KF8), the newer format. .azw is an older Amazon extension that store downloads often use, and those files are usually DRM-protected. The checker tells you which one you have and whether it is encrypted.

Should I translate MOBI or EPUB if I have both?

Translate the EPUB. It is the better source in most cases, and the translated EPUB works with Send to Kindle, other reading apps, and KDP. Use the MOBI only if it is all you have and you will read on a Kindle.

Can I use the translated MOBI to publish on Amazon?

No. KDP no longer accepts MOBI files. Convert the original to EPUB, translate the EPUB, have it reviewed, and upload the EPUB or a DOCX.