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Our free online eBook converter supports popular formats including EPUB, MOBI, AZW3, PDF, FB2, and CBZ comic book archives. All conversions happen in your browser, ensuring your books remain private.
Whether you need to convert books for your Kindle, Kobo, Apple Books, or other e-readers, our tool preserves formatting, table of contents, and cover images during conversion.
eBook formats differ in how they store text, images, and metadata, and each e-reader ecosystem has its own preferred format. Understanding these differences helps you choose the right format for your device and reading preferences.
EPUB is the most widely supported open eBook standard, maintained by the W3C. It uses reflowable content, meaning text automatically adjusts to fit your screen size, whether you are reading on a phone, tablet, or dedicated e-reader. EPUB supports embedded fonts, images, CSS styling, and interactive elements. EPUB 3, the current version, also supports audio, video, and JavaScript. Nearly every e-reader and reading app supports EPUB except Amazon Kindle devices, which require conversion to a Kindle-compatible format.
MOBI was originally developed by Mobipocket SA and later acquired by Amazon. It was the primary Kindle format before AZW3 replaced it. MOBI supports basic formatting, bookmarks, and annotations, but lacks many features available in EPUB 3 and AZW3 such as advanced CSS, embedded fonts, and HTML5 elements. Amazon officially stopped accepting MOBI uploads in 2022, but millions of existing MOBI files still circulate. If you have MOBI files, converting them to EPUB or AZW3 will give you better formatting and features.
AZW3, also called KF8, is Amazon's current eBook format for Kindle devices and apps. It supports HTML5, CSS3, embedded fonts, and rich formatting that was impossible in the older MOBI format. AZW3 files can include DRM (digital rights management) when purchased from Amazon, but DRM-free AZW3 files can be freely converted to other formats. If you are creating eBooks for Kindle, AZW3 is the recommended format.
PDF preserves exact page layouts, which makes it suitable for textbooks, academic papers, and graphic-heavy publications where layout matters. However, PDF is a fixed-layout format, which means it does not reflow text to fit different screen sizes. Reading a PDF on a small e-reader or phone often requires zooming and scrolling, which creates a poor reading experience for text-heavy books. Use PDF for eBooks only when precise layout preservation is more important than reading comfort.
Digital Rights Management (DRM) is copy protection applied to eBooks purchased from major retailers. DRM-protected files cannot be converted to other formats, even with legitimate tools. This means a DRM-protected Kindle book cannot be converted to EPUB for a Kobo reader. Browser-based converters, including ours, can only convert DRM-free eBook files. If you purchase DRM-free eBooks from stores like Smashwords, Google Play Books (some titles), or Tor.com, you can freely convert between formats.
Reflowable eBooks (EPUB, MOBI, AZW3) adjust text and images to fit any screen size, letting readers change font sizes and margins. Fixed-layout eBooks (PDF, some EPUB 3 files) preserve exact page positioning, which is essential for children's books, comics, cookbooks, and textbooks with complex layouts. When converting between these two types, expect significant layout changes since the fundamental approach to page rendering is different.
| Format | Primary Reader | Reflowable | DRM Support | Best For |
|---|---|---|---|---|
| EPUB | Kobo, Apple Books, Google Play Books, most readers | Yes | Adobe DRM, Apple FairPlay | Universal standard, non-Kindle devices |
| MOBI | Older Kindle devices | Yes | Amazon DRM | Legacy Kindle compatibility |
| AZW3 | Kindle devices and apps | Yes | Amazon DRM | Kindle users, rich formatting |
| Any device with PDF viewer | No (fixed layout) | Adobe DRM, password protection | Textbooks, academic papers, graphic-heavy content | |
| FB2 | FBReader, CoolReader, popular in Russia/Eastern Europe | Yes | None | Fiction, clean XML-based structure |
| CBZ | Comic book readers (CDisplayEx, YACReader) | No (page images) | None | Comics, manga, graphic novels |
Kindle devices and apps natively support AZW3, MOBI, and PDF. For the best reading experience, use AZW3, which supports advanced formatting and reflowable text. If you have an EPUB file, convert it to AZW3 before transferring to your Kindle. You can also send EPUB files to your Kindle via Amazon's Send to Kindle service, which automatically converts them.
Kobo e-readers natively support EPUB and PDF. EPUB is the preferred format since Kobo's software is optimized for it, providing excellent typography and reading customization. If you have Kindle-format books (AZW3 or MOBI), convert them to EPUB for the best experience on Kobo.
Apple Books supports EPUB and PDF. EPUB is strongly recommended for text-heavy books because Apple Books provides a polished reflowable reading experience with customizable fonts, themes, and margins. Use PDF only for fixed-layout content like textbooks or graphic novels.
For reading apps on Android or iOS (such as Google Play Books, Libby, or Moon+ Reader), EPUB is the most versatile choice. It reflows cleanly across screen sizes, and nearly every reading app supports it. Avoid PDF for long-form reading on small screens since the fixed layout requires constant zooming and panning.
If you are publishing an eBook, create an EPUB master file. Most retailers (Apple Books, Google Play, Kobo, Smashwords) accept EPUB directly. For Amazon KDP, upload the EPUB and Amazon will convert it for Kindle. Having a clean EPUB source makes it easy to distribute across all platforms with a single conversion step.
Only if the Kindle book is DRM-free. Books purchased from Amazon's Kindle Store are typically protected by Amazon's DRM, which prevents conversion to other formats. DRM-free AZW3 or MOBI files, such as those from personal documents or DRM-free publishers, can be freely converted to EPUB using browser-based tools like ours. Amazon does not sell DRM-free books on most titles, so check the book's rights information before attempting conversion.
EPUB is an open standard supported by virtually every e-reader except Kindle, while MOBI is a proprietary Amazon format designed for older Kindle devices. EPUB supports richer formatting, embedded fonts, HTML5, CSS3, and interactive elements. MOBI is limited to basic formatting and has been deprecated by Amazon in favor of AZW3. For most purposes, EPUB is the superior format unless you specifically need compatibility with very old Kindle devices.
Some formatting loss is possible depending on the conversion. Converting between reflowable formats (EPUB to AZW3, for example) usually preserves text, chapters, and basic styling well. Converting from a reflowable format to PDF will lock the layout at a specific page size, which may look different from the original reading experience. Converting from PDF to EPUB is the most lossy because the converter must reconstruct a reflowable layout from a fixed one. Cover images, tables of contents, and chapter headings are generally preserved across all conversions.
EPUB 3 is the most feature-rich open eBook format, supporting HTML5, CSS3, SVG graphics, embedded fonts, audio, video, JavaScript interactivity, mathematical notation (MathML), and accessibility features like text-to-speech hints. AZW3 supports a comparable feature set on Kindle devices. MOBI and FB2 are more limited, supporting only basic text formatting. For maximum feature support across the broadest range of devices, EPUB 3 is the best choice.
Kindle devices do not natively support EPUB, but there are two practical workarounds. First, you can convert your EPUB to AZW3 using a converter tool, then transfer the file to your Kindle via USB or the Send to Kindle app. Second, since late 2022, Amazon's Send to Kindle service accepts EPUB files and automatically converts them for your Kindle. Simply email the EPUB file to your Kindle email address or use the Send to Kindle app, and the converted book will appear in your Kindle library.