EPUB, MOBI, AZW3, PDF: which ebook format to use
A plain guide to the formats your reader accepts, which one to keep your books in, and when conversion helps or hurts.
Last updated August 2026
The formats you will meet
- EPUB — the open standard. Reflowable text, works on everything except older Kindles directly. Keep your library here if you can.
- KF8 / AZW3 — Amazon’s format. Effectively EPUB in a different wrapper. Convert to this for Kindle.
- MOBI — the old Kindle format. Being retired; avoid for new files.
- PDF — fixed layout. Great for documents and comics, poor for novels on a small screen because the text cannot reflow.
- CBZ / CBR — zipped images for comics and manga.
Rules of thumb
- Store originals in EPUB. It converts cleanly to anything else later.
- Convert to AZW3 only when sending to a Kindle, and keep the EPUB.
- Do not convert a PDF to EPUB expecting good results — the layout rarely survives. Use your reader’s PDF reflow mode instead.
- Every conversion can introduce small formatting errors. Convert once, from the best source you have, not repeatedly.
DRM
Books bought from a store are often locked to that store’s app. That is a licensing question, not a format one, and this site does not cover removing it.