Free Online Ebook Converter
Convert between ebook formats online for free. Supports EPUB, MOBI, AZW3, FB2, LIT, PDB, CBR, CBZ and more. Fast, secure, browser-based conversion with no software to install.
| ファイル名 | サイズ | 変換先 |
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ファイルと選択した出力形式を確認しています。
About Free Online Ebook Converter
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
| フォーマット | Reflowable | Native reader | こんな方に最適 |
|---|---|---|---|
| EPUB | はい | Apple Books, Kobo, Google Play Books, Calibre | The open standard — first choice for non-Kindle |
| AZW3 / MOBI | はい | Kindle only | Sideloading to Kindle devices |
| No (fixed layout) | Every device | Fixed layouts — technical books, cookbooks, comics | |
| FB2 | はい | Cool Reader, Pocketbook, Calibre | Common in Eastern-European libraries |
| LIT / LRF / PDB | はい | Legacy readers only | Only if you inherited an older library |
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 固定レイアウト 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? に変換 EPUB. It's the industry standard and works everywhere except Amazon's ecosystem.
- Sideloading to a Kindle? に変換 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? に変換 PDF. Nothing else guarantees pixel-exact layout across readers.
- Digitising a PDF for reading on a phone? に変換 EPUB ほとんどがテキストの場合。画像がほとんどである場合、複雑なレイアウト、または数式が含まれている場合は、PDF を保持します。
- 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
Kindle、Apple Books、Google Play Books、または Kobo からダウンロードしたファイルは、DRM で保護されている可能性があります。この保護はファイル レベルで適用されます。たとえ形式が EPUB や AZW3 のように見えても、コンバーターはコンテンツを読み取ることができません。ソースが商用ストアから提供されたものである場合、変換を可能にする前に、DRM フリーのソース (Project Gutenberg、Standard Ebooks、Smashwords、ほとんどのインディーズ著者のサイト) から書籍を購入してダウンロードする必要があります。
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.
How to convert an ebook, step by step
Same flow for every ebook tool below — EPUB to MOBI, MOBI to EPUB, PDF to EPUB, and back.
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1
ソースとターゲットに応じてツールを選択する
Start with what you have. EPUB downloaded from Project Gutenberg? Old MOBI from an early Kindle purchase? PDF of a public-domain novel? Each dedicated tool page is tuned for that specific pair and handles the format quirks (chapter markers, cover art placement, metadata mapping) automatically.
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2
Upload your ebook
Most ebook files are small — a typical novel is 1-3 MB, well within the free-tier 10 MB cap. Illustrated books, textbooks, or scanned PDFs can be much larger; those need a Pro plan for anything over 10 MB. Batch conversions of up to 20 files are handy for cleaning up a legacy library in one pass.
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3
Let the defaults do their thing (usually)
Ebook conversions have far fewer knobs than image or video. The tool preserves structure and metadata by default. Where a setting matters — say, converting a scanned PDF where you'd rather keep the images than force text reflow — the tool page calls it out with a one-line explanation.
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4
Convert, download, and side-load
The output is ready in a few seconds. Download to your device, then move the file to your reader: Books.app on iPhone/iPad, Send-to-Kindle for Amazon devices, or drop it directly into Calibre for a full library workflow. Both the upload and the converted files are deleted within 30 minutes.
Tips people usually learn the hard way
- DRM-protected files won't convert. If your ebook came from Kindle, Apple Books, Google Play Books, or Kobo, it's likely locked. Buy or find a DRM-free copy first — Standard Ebooks, Project Gutenberg, and most indie authors' sites offer them.
- PDF-to-EPUB is best-effort on scanned books. If the PDF is text-based (searchable), conversion works cleanly. If it's a scanned image PDF, the result is an EPUB full of images — technically valid, but a poor reading experience on a phone.
- Send to Kindle now accepts EPUB. Amazon updated the flow — you no longer need to convert EPUB to AZW3 unless you want fine control. EPUB via Send-to-Kindle just works.
- ソースを保存してください。 Always keep a copy of the original file. If a conversion has an issue you notice weeks later, you can re-convert without hunting down the source again.
When you actually need to convert an ebook
フォーマットの交換がすべての仕事である 6 つの正直なシナリオ。
Moving a library between reader ecosystems
Bought a Kobo after years of Kindle? Switching from Amazon to Apple Books? Your existing MOBI or AZW3 collection needs to become EPUB (or PDF) to work outside Amazon's ecosystem. Converting the whole library in one batch is a common one-time job when someone changes devices.
Reading a PDF novel on a phone without pinch-to-zoom
A PDF-formatted book on a phone screen is a rough experience — text is too small to read at native zoom, and swiping between pages feels clunky. Converting to EPUB reflows the text to fit the screen, making the same book actually readable. Works well for text-heavy content; less well for anything layout-driven.
Sideloading a public-domain book to your Kindle
Project Gutenberg offers most books as EPUB. Getting them onto a Kindle used to require converting to AZW3 first, but Amazon's Send-to-Kindle now handles EPUB directly. Convert to AZW3 only if you want tight control over the formatting on the Kindle.
Consolidating a legacy library to one format
If you've been collecting ebooks for a decade, chances are the library is a mess: LIT files from an old reader, FB2 from a Russian archive, MOBI from an early Kindle, EPUB from newer sources. Converting everything to EPUB (the only ebook format with real 2026-onward support) gives you one archival master that every reader on the market can open.
Preparing your own writing for readers
Writers and self-publishers often work in Word or Google Docs, then need to convert to EPUB for distribution and AZW3 for Kindle Direct Publishing. Converting from DOCX to EPUB (with a quick clean-up pass in the reader) is usually the fastest path from manuscript to shippable ebook.
Making a textbook portable across devices
Academic PDFs are usually fine at a laptop or tablet size, but painful on phones. Converting to EPUB works well when the textbook is mostly prose; keep the PDF if the book leans heavily on tables, equations, or diagrams that would break on reflow. Some students keep both — EPUB for reading, PDF for reference.
Not sure which conversion fits your case? Skim the grid below — each entry is labelled with source and target format and includes a note on what to expect from the result.