What is the best ebook format in 2026?

EPUB 3 is the best ebook format for reading in 2026. It's an open W3C standard supported by every major reading platform: Apple Books, Kobo, Google Play Books, Kindle (since 2022), Nook, and all major reading apps. Text reflows to your screen size and font preferences, supports accessibility standards, and allows MathML for equations.

Is EPUB or PDF better for ebooks?

EPUB is better for reading on screens. EPUB text reflows to your preferred font size and screen width, supports night mode, adjustable fonts, and accessibility tools. PDF text is fixed at pixel-precise positions and cannot reflow, making it difficult to read on phones and e-readers. Use PDF only for print-ready documents or when exact layout must be preserved.

Is MOBI still a good ebook format?

No. Amazon deprecated MOBI in August 2022 — Send to Kindle no longer accepts MOBI files and KDP (Kindle Direct Publishing) no longer accepts MOBI for new titles. For Kindle, use EPUB instead. Existing MOBI files already on Kindle devices still work, but you cannot add new ones via email or the Send to Kindle service.

What format does Kindle use internally?

Kindle devices store books in AZW3 (also called KF8). When you send an EPUB to Kindle via email or the Send to Kindle website, Amazon automatically converts it to AZW3 for delivery. When you purchase from the Kindle Store, the file arrives as AZW3. You don't need to create AZW3 yourself — just send EPUB and Amazon handles the conversion.

Best Ebook Format in 2026: EPUB, PDF, MOBI, or AZW3?

There are half a dozen ebook formats in common use and each has different device support, features, and use cases. Here's a plain-language breakdown of every format and when to use each one.

Quick answer

For reading on any device: EPUB 3
For Kindle: EPUB 3 (send to Kindle) or AZW3 (purchased from Amazon)
For printing or fixed layout: PDF
For old Kindle devices via USB: MOBI (legacy only)

EPUB 3 — the universal standard

EPUB 3 is the open international standard for ebooks, published by the W3C. It is supported by:

Apple Books (iPhone, iPad, Mac)
Kobo (all devices)
Google Play Books
Kindle (since 2022)
All major reading apps (Thorium, Calibre, Moon+ Reader, Libby)

Strengths: Reflowable text, adjustable fonts, accessibility (WCAG/EPUB Accessibility 1.1), MathML for equations, SVG for diagrams, media overlays for audio narration, open and non-proprietary.

Limitations: Fixed-layout EPUBs (comics, illustrated books) need more work to produce correctly.

EPUB 3 is the right choice for virtually all text-based reading material.

PDF — fixed layout, print-ready

PDF locks content into exact page positions. Every element is placed at pixel-precise coordinates.

Strengths: Identical rendering on every device, preserves exact design, ideal for printing, widely supported everywhere.

Limitations: Font size cannot be adjusted, text doesn't reflow on small screens, poor screen reader support for complex layouts, two-column PDFs are nearly unreadable on phones.

When to use PDF: Sharing documents that must look exactly the same for everyone (forms, invoices, design-heavy reports), printing, archiving to PDF/A standard.

When NOT to use PDF for reading: Phones, e-readers, tablets in portrait mode — the text will be too small and won't reflow.

MOBI — deprecated (Amazon, legacy)

MOBI was Amazon's Kindle format before EPUB support. Amazon deprecated MOBI in August 2022:

Send to Kindle no longer accepts MOBI files
KDP no longer accepts MOBI for publishing
Existing MOBI files on Kindle devices still work

Use today: Only for USB sideloading to very old Kindle devices. For anything new, use EPUB.

See EPUB vs MOBI full comparison →

AZW3 (KF8) — Amazon Kindle native format

AZW3 is what Kindle devices actually store internally. When you send an EPUB to Kindle, Amazon converts it to AZW3 for delivery. When you buy from the Kindle Store, the file is AZW3.

You do not need to create or handle AZW3 files directly — Amazon handles the conversion. Just send EPUB to Kindle.

FB2 — popular in Russia and Eastern Europe

FB2 (FictionBook) is an XML-based format popular in Russian-language ebook communities. Calibre and many Android/desktop readers support it. Not relevant for most Western users.

CBZ / CBR — comics and manga

CBZ and CBR are ZIP/RAR archives of sequential images — used for comics and manga. Not text-based and not convertible from PDF in any meaningful way.

Format comparison table

Format	Reflowable	Kindle	Kobo/Apple	Open standard
EPUB 3	Yes	Yes (2022+)	Yes	Yes (W3C)
PDF	No	Poor	Poor	Yes (ISO)
MOBI	Yes	Deprecated	No	No (Amazon)
AZW3	Yes	Yes (native)	No	No (Amazon)
FB2	Yes	No	Partial	Yes

Converting between formats

If you have a PDF and want to read it on any device as a proper ebook, convert it to EPUB:

Go to toolkit.bot/pdf2epub — free, no account, handles academic layouts and scanned pages
Upload your PDF, download the EPUB
Open in any reading app or send to Kindle

Have a PDF? Convert it to EPUB — the universal reading format.

Convert PDF to EPUB →