What to send to Kindle: EPUB, AZW3, or MOBI

Send to Kindle wants EPUB. A USB copy wants AZW3. MOBI is no longer accepted by Send to Kindle.

A Kindle has two different ways to receive a personal document. Send to Kindle converts the file again on Amazon's servers. A USB copy is opened by the device as-is. Choose the format for the path you will actually use.

Which format should you send to Kindle?

When you email a personal document, or send it from the app or the website, prefer EPUB. Amazon converts it into Kindle's own format and delivers that to the device.

That service accepts EPUB, and it also accepts PDF, DOCX, and TXT. It does not accept MOBI anymore. If you only have MOBI, convert it to EPUB with MOBI converter, then send the EPUB. How the three formats differ is in EPUB vs MOBI vs AZW3.

You can send a PDF without converting it. The page will not reflow, which is fine for comics or a designed layout and poor for a novel on a small screen. When to convert first is covered in PDF to EPUB.

Which format should you copy over USB?

When you put a file in the Kindle documents folder over a cable, the device tries to open that file. Amazon does not convert it in between.

  • AZW3 is the safer choice. The table of contents and images survive better than in MOBI. Make it with AZW3 converter.
  • EPUB often will not open after a USB copy. The file is not corrupt. The device simply does not treat EPUB as a USB import format.
  • MOBI is only worth it for a very old device. On newer ones it is usually a worse file than AZW3.
  • PDF opens, but as a fixed page. Type size and line breaks do not follow the screen.

If the old file is AZW rather than AZW3, convert it on its own. AZW converter can turn it into AZW3 or EPUB.

How do you do it?

  1. Open ebook converter.
  2. Drop EPUB, MOBI, AZW3, AZW, PDF, DOCX, or TXT. The limit is 50MB per file.
  3. For a Kindle email address, choose EPUB. For a USB copy, choose AZW3.
  4. Start conversion and stay on the page. Large files wait in a queue. Download from this page when it finishes.
  5. Send that download with Send to Kindle, or copy it over USB.

A Word manuscript should not be printed to PDF first. Converting the DOCX is cleaner. See Word and TXT to EPUB.

Which files will not convert?

  • DRM-locked purchases, including many books downloaded from the Kindle store. There is no readable text inside. Renaming the file does nothing. This site cannot remove DRM.
  • KFX, the newer Kindle package. It is not in the supported list.
  • Files over 50MB. Image-heavy PDFs and EPUBs hit this often. Split them or reduce the images first.

Each conversion uses 1 free quota credit. Upload and download do not cost an extra credit.

The matching how-tos: EPUB to AZW3 for USB, EPUB to MOBI only for a very old device, and AZW3 to EPUB when you are leaving Kindle. The format comparison is EPUB vs MOBI vs AZW3.

Common questions

Can I still Send to Kindle a MOBI file?

No. Amazon stopped accepting MOBI in Send to Kindle in 2022. Send EPUB instead, or send PDF, DOCX, or TXT.

EPUB copied over USB will not open on my Kindle. Why?

Many Kindles do not open EPUB files placed there over USB. Convert the EPUB to AZW3 and copy that, or use Send to Kindle and let Amazon convert the EPUB in the cloud.

Why won't a purchased Kindle book convert?

Store purchases are usually DRM-locked. The converter cannot read the text, so it cannot produce EPUB or anything else. The filename, AZW or KFX, does not change that.

Keep reading

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EPUB, MOBI, AZW3, AZW, PDF, FB2, TXT, DOCX, HTML, and RTF. Up to 50MB per file. Nothing to install.

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