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Use EPUB for reading on phones, tablets, Kobo and almost every ebook app, and for sending books to a Kindle by email or the Send to Kindle app. Use PDF when the page layout matters or you want to print. MOBI and AZW3 are older Kindle formats that are mainly useful for copying books to a Kindle over USB.
The short comparison
| EPUB | MOBI | AZW3 (KF8) | ||
|---|---|---|---|---|
| Text resizes to the screen | Yes | No, fixed pages | Yes | Yes |
| Good for small phone screens | Yes | Only for small page sizes | Yes | Yes |
| Keeps an exact page layout | No | Yes | No | No |
| Good for printing | No | Yes | No | No |
| Kobo, Apple Books, Google Play Books | Yes | Yes, as fixed pages | No | No |
| Kindle via Send to Kindle or email | Yes | Yes, as fixed pages | No longer accepted | No |
| Kindle via USB cable | No | Yes | Yes | Yes |
Reading on a Kindle
Amazon’s Send to Kindle service, including the email address and the apps, takes EPUB and converts it for the device. It stopped accepting MOBI. So if you have a DRM-free EPUB, send it as it is.
If you prefer to copy files over a USB cable, a Kindle reads MOBI and AZW3 directly, but not EPUB. That’s the one case where converting with EPUB to MOBI is worth it, mostly for older Kindles.
A PDF also works on a Kindle, but a page made for A4 or Letter paper is shrunk to fit a 6- or 7-inch screen, which makes the text small. For a text PDF you plan to read on a Kindle, PDF to EPUB gives you text that reflows.
Reading on a phone
EPUB, in an app such as Apple Books, Google Play Books or a Kobo app. Reflowing text means you can raise the font size without scrolling sideways. A PDF on a phone means zooming and panning on every page, unless it was made at a small page size.
If you have Kindle files and no Kindle, MOBI to EPUB and AZW3 to EPUB turn DRM-free copies into EPUBs that open in those apps.
Printing, citing and marking up
PDF. Its pages are the same on every device, so page 112 is page 112 for everyone, which matters when you cite a book or print it. EPUB to PDF lays the book out on A5, 6 × 9 in, A4 or US Letter pages, with page numbers. For Kindle files, MOBI to PDF does the same and also reads AZW3.
What changes when you convert
- EPUB or MOBI to PDF: the book gets fixed pages at the size you pick. The book’s own fonts and styling are replaced by the font you choose, and fixed-layout books such as comics lose their page design.
- PDF to EPUB or MOBI: the text is rebuilt as paragraphs. This works well for novels and reports with one column of text. Tables, footnotes and multi-column pages come out flattened, and scanned PDFs can’t be converted because there’s no text inside them.
- MOBI or AZW3 to EPUB: usually the cleanest conversion, since both are reflowable formats.
DRM: the thing no converter changes
Books bought from Kindle, Kobo or Google Play are usually locked to that store’s apps with DRM. None of the converters here open DRM-protected books; they show a message saying so. Free public-domain books, your own documents and DRM-free purchases convert fine.
Quick answers
- Kindle, sending wirelessly: EPUB.
- Kindle, USB cable: AZW3 or MOBI.
- Phone, tablet, Kobo: EPUB.
- Print or fixed pages: PDF.
- Keeping an archive: EPUB for books, PDF for documents where layout matters.