Kindle reads several formats, but .mobi and .azw are the native ones

Amazon's Kindle devices and apps read .azw, .azw3, and .mobi files natively — meaning you can load them directly onto a Kindle without conversion. Of these, .azw3 is the current standard for new Kindle books. The older .mobi format still works on all Kindle devices, but Amazon phased it out for new releases around 2014. If you're buying from Amazon's store, you get .azw or .azw3 automatically.

The practical difference: .azw3 handles modern formatting better — fonts, images, and layouts render more reliably — while .mobi is simpler and works on older Kindle models. Both are proprietary Amazon formats, which means they're encrypted to prevent copying and tied to your Amazon account.

Key Takeaways

  • Kindle natively reads .azw, .azw3, and .mobi files; .azw3 is the current standard for new books.
  • You can also send .pdf, .doc, .docx, .txt, and .html files to your Kindle email address and Amazon converts them automatically.
  • Project Gutenberg and many library systems distribute books in .mobi or .epub, so you may need to convert .epub files using free tools like Calibre before loading them onto a Kindle.
  • DRM (digital rights management) encryption on .azw and .azw3 files ties them to your Amazon account and prevents sharing.
  • If you want to read the same book across multiple devices without buying it twice, .pdf and .txt files work on nearly everything, though formatting may vary.

What Kindle will accept if you email it directly

Amazon lets you email documents to your Kindle device using a special email address tied to your account. When you do, Amazon converts the file and pushes it to your device wirelessly. The formats that work this way are: .pdf, .doc, .docx, .txt, .html, .rtf, .jpeg, .gif, .png, .bmp, and .svg.

This is useful if you have a Word document, a text file, or a web article you want to read on your Kindle. The conversion is automatic, but the formatting may not be perfect — especially with .pdf files, which sometimes render with odd spacing or margins on small screens. You can find your Kindle email address in the Amazon account settings under "Devices and Content" > "Your Devices" > select your device > "Send-to-Kindle Email Address".

Why .epub files don't work on Kindle without conversion

.epub is the open standard for e-books and is used by almost every other e-reader: Apple Books, Kobo, Google Play Books, and most library lending systems. Kindle deliberately does not read .epub, which forces readers to either buy from Amazon or convert files manually.

If you have an .epub file and want to read it on Kindle, you need to convert it first. The free tool Calibre (calibre-ebook.com) does this reliably. Open Calibre, add your .epub file, click "Convert books", set the output format to .azw3, and save. Then email the converted file to your Kindle address or plug your device into a computer and drag the file into the Kindle folder.

This extra step is why many people use a different e-reader if they borrow heavily from libraries — Kobo and Tolino devices read .epub natively, so no conversion is needed.

DRM encryption and what you can and cannot do with Kindle files

.azw and .azw3 files from Amazon's store are encrypted with DRM (digital rights management). This encryption ties the file to your Amazon account and prevents you from sharing it, lending it, or reading it on non-Kindle devices without removing the encryption first.

Books you convert yourself or email to Kindle as .pdf or .txt files have no DRM, so you can move them freely between devices. Library books borrowed through Kindle also have DRM, but it expires when the loan period ends — the book straightforward stops working on your device after the due date.

Removing DRM from Amazon books is technically possible but violates the Digital Millennium Copyright Act in the United States, even for books you own. Many readers do it anyway to read on other devices, but it carries legal risk.

Where to find books in formats Kindle actually reads

Project Gutenberg (gutenberg.org) offers over 70,000 public-domain books in .mobi, .epub, .html, and .txt. You can read .mobi files directly and load them onto your Kindle with no conversion needed. Standard Ebooks (standardebooks.org) does the same with a smaller, carefully edited collection.

Most public libraries now lend e-books through OverDrive or Libby (the newer app). These systems let you borrow books in .epub format, which you then convert to .azw3 using Calibre before loading onto Kindle. Some libraries also offer Kindle lending directly through Amazon, which skips the conversion step entirely — ask your library whether they participate.

If you're buying new books, Amazon's Kindle Store delivers .azw3 files automatically. For older or self-published books, check whether the seller offers .mobi as a read option before buying.

How file format affects reading across multiple devices

If you want to read the same book on a Kindle, a phone, and a tablet without buying it three times, file format matters. .pdf and .txt files work on nearly everything, though .pdf may display awkwardly on small screens. .epub works on Apple Books, Kobo, Tolino, and most library apps, but not Kindle.

.azw and .azw3 files work only on Kindle devices and the Kindle app — they won't open in Apple Books or any other reader. This is by design: Amazon's encryption locks you into their ecosystem. If you value flexibility, stick with .pdf, .txt, or .epub for books you own outright, and use Kindle only for books you're borrowing or buying from Amazon.

Some readers solve this by keeping two copies: an .azw3 for Kindle and an .epub for everything else. It's not ideal, but it's the only way to get the same book onto multiple platforms without DRM removal.

Frequently Asked Questions

Can I read a Kindle book on my phone or computer?

Yes, if you install the free Kindle app from Amazon. The app works on iPhone, Android, Mac, Windows, and web browsers. Your .azw and .azw3 files sync across all your devices through your Amazon account, so you can start reading on your Kindle and pick up where you left off on your phone.

What happens if I convert an .epub to .azw3 using Calibre — does it still have DRM?

No. When you convert a file yourself, the output has no DRM. You can move it freely between devices and share it. DRM only comes from Amazon's store or from library lending systems — it's not added by the conversion process.

Do I need to use Calibre, or are there other conversion tools?

Calibre is the most reliable free option and works on Windows, Mac, and Linux. Online converters like CloudConvert and Zamzar also work, but they upload your file to their servers, which is a privacy concern if the book contains personal notes or highlights. Calibre runs locally on your computer.

If I buy a book from Amazon in .azw3, can I read it on a Kobo reader?

Not without removing the DRM encryption first, which is legally risky in most countries. If you want to read across multiple devices, buy from a DRM-free seller or borrow from your library in .epub format and convert it yourself.

Why does my .pdf look weird on my Kindle?

Kindle's small screen doesn't handle .pdf well — the text may be tiny, margins may be wrong, or images may not fit. For better results, convert the .pdf to .azw3 using Calibre, which reflows the text to fit the screen. This works best for text-heavy documents; image-heavy .pdfs still look poor on small screens.