Free Online Ebook Converter — EPUB, MOBI, AZW3, FB2

Ebook conversion is a category most people run into once, get confused by, and then avoid — because the ebook format landscape is more fragmented than any other file type. Between Amazon's proprietary formats, Apple's preference for EPUB, the resurgence of PDF-as-book, and a dozen legacy formats still floating around, the "just convert it" instinct often lands you with a file your device politely refuses to open.

This overview covers what each ebook format actually is, which reader supports what, and how to convert without losing the parts of a book that matter — chapter structure, table of contents, embedded images, and readable typography.

The five formats that actually matter in 2026

Reflowable vs. fixed — the single biggest choice

A reflowable ebook (EPUB, AZW3, MOBI, FB2) is essentially a small website: HTML content that a reader wraps into whatever page shape and font size the user prefers. Turning up the text size doesn't zoom in — it re-flows the paragraphs. That's the reading experience most people expect from an ebook.

A fixed-layout format (PDF, or fixed-layout EPUB) treats every page as an image. Layout is preserved exactly — good for cookbooks, comics, and children's books — but text doesn't reflow, so on a small screen you're pinching to zoom. Converting a PDF novel into an EPUB usually improves the reading experience dramatically; converting an illustrated cookbook the same way often breaks the layout.

Choosing a target — a short decision tree

• Reading on any non-Kindle device? Convert to EPUB. It's the industry standard and works everywhere except Amazon's ecosystem.
• Sideloading to a Kindle? Convert to AZW3. Amazon accepts EPUB via "Send to Kindle" now, but AZW3 gives you finer control over formatting.
• Sharing a book that must look identical on every device? Convert to PDF. Nothing else guarantees pixel-exact layout across readers.
• Digitising a PDF for reading on a phone? Convert to EPUB if it's mostly text. Keep the PDF if it's mostly images, complex layouts, or contains equations.
• Cleaning up a legacy library? Convert everything to EPUB as your archival master. It's the only ebook format with a real future.

What survives (and what doesn't) in an ebook conversion

A well-executed ebook conversion preserves chapter structure, table of contents, inline images, italics and bold, and paragraph breaks. It rarely preserves complex layouts (multi-column pages, sidebars, footnotes on the same page as the reference), custom fonts, or drop caps and other typographic flourishes.

For most novels and non-fiction, this trade-off is invisible. For textbooks, cookbooks, and illustrated books, the layout loss is real. If a book relies heavily on how it's arranged on the page, keep it as PDF.

DRM — the reason "just convert it" sometimes fails

A file downloaded from Kindle, Apple Books, Google Play Books, or Kobo is likely DRM-protected. That protection is enforced at the file level: even if the format looks like EPUB or AZW3, a converter won't be able to read the content. If your source came from a commercial store, you'll need to purchase and download the book from a DRM-free source (Project Gutenberg, Standard Ebooks, Smashwords, most indie authors' sites) before conversion is possible.

What every iFormat ebook converter does the same way

All the tools listed below process ebooks on isolated per-request workers, with TLS-encrypted uploads and 30-minute auto-delete on both source and output. Table of contents, chapter breaks, and inline images are preserved by default across supported format pairs. Metadata (title, author, publisher, cover art) carries through wherever the target format supports it.