Ebook File Formats Explained Without the Nonsense
Learn the difference between EPUB, PDF, MOBI and AZW3, and choose the format that works with the device you actually use.
EPUB is the normal choice for a book people will read on phones, tablets and most e-readers. PDF is the choice when every page must stay in exactly the same place. Kindle can read EPUBs sent through its current book-delivery tools, even though the file on the device may be converted internally.
You do not need to learn every ebook format before converting a manuscript. Start with where the book will be read and whether the text needs to resize for the screen.
The four formats you are most likely to meet
EPUB is a reflowable ebook, which means the words move when the reader changes the font size or screen width. PDF keeps fixed pages. MOBI is an older Kindle format you may still find in an old library. AZW and KFX are Kindle formats usually handled by Amazon's own apps and delivery system.
For a new general ebook, make EPUB. For a printable workbook, form, comic layout or document that must keep exact pages, make PDF as well.
How to choose the output
Choose the reading device or store
Check what the place you are sending the book to accepts. Do not convert until you know the destination.
Decide whether the text should resize
Choose EPUB for normal novels and text-heavy books. Choose PDF when fixed page design matters more.
Convert from the best source
Use the original Word or Markdown manuscript when possible, rather than converting from a PDF that has already fixed every line onto a page.
Open the result like a reader
Change the font size, use the chapter menu, tap links and check images. For PDF, check the actual page size and print layout.
Common problems
The book is tiny on a phone
It is a fixed PDF page being squeezed onto a small screen.
Provide an EPUB for normal reading.
The EPUB page count keeps changing
The reader is resizing and reflowing the text.
That is normal; use chapters or sections rather than fixed page references.
An old MOBI looks odd
It came from an older ebook workflow with limited styling.
Return to the original manuscript and make a new EPUB.
Frequently asked questions
What is the best format for an ebook?
EPUB for most text-heavy books. Add PDF when readers also need fixed pages or printing.
Can Kindle read EPUB?
Amazon's current send-to-Kindle services accept EPUB and convert it for Kindle reading. Check Amazon's current file requirements before publishing.
Is PDF an ebook?
It can be read electronically, but it behaves like a fixed page rather than a normal reflowable ebook.
Should I convert an old MOBI to EPUB?
Yes if you only have MOBI, but the original Word, HTML or Markdown source will usually make a cleaner EPUB.
Extra: What reflowable and fixed layout mean
Reflowable text behaves like a normal webpage: paragraphs adapt to the screen. That makes an EPUB comfortable on both a phone and a large tablet, but page numbers and line breaks can change.
A fixed-layout book keeps each item in a set position. It can suit illustrated children's books, comics and textbooks, but it is harder to read on a small screen. A PDF is the common fixed-page version, while EPUB also has a specialist fixed-layout mode.
