Top 15 eBook File Formats You Should Know for Seamless Reading
To give readers a smooth reading experience across devices you have to choose the right eBook file format as it can affect accessibility and compatibility with publishing platforms. In our guide, we break down the top eBook formats, their pros and cons and which one suits you best.
Not all eBooks are created equal, neither are their file formats. So, the format you choose (whether you’re a casual reader, a self-publishing author or a business distributing digital content) can make or break the reading experience. We have come up with this guide to discuss the most popular eBook file formats you need to know, how they differ and which one will suit your needs the best.
Why eBook File Formats Matter
- The eBook format you choose determines compatibility with different devices (Kindle, iPad, Android, Windows, etc.)
- Whether or not the file format supports reflowable text vs. fixed layouts determines the reader experience
- Distribution is also affected because not all devices or platforms support all eBook file formats.
- The file type also affects file size, multimedia support and accessibility of the content
Quick note: Amazon recently stopped support for MOBI in favor of EPUB, so your format choice is more crucial than ever.
Top 15 eBook Formats and their Differences
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EPUB
File Extension: .epub
Image Support: Available
Audio Support: Available
Video Support: Available
DRM Support: Yes
What it is:An open-source, industry standard e-book format supported by almost all platforms like Apple Books, Kobo, Nook, Google Play Books, Kindle (after automatic conversion) and many others.
What it’s best for:Most readers and publishers.
Key benefit:Can display content in both reflowable and fixed layouts and also supports multimedia.
Limitation:It won’t work on older models of Kindle devices.
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Mobipocket
File Extension: .mobi
Image Support: Available
Audio Support: Not available
Video Support: Not available
DRM Support: Yes
File Extension: .prc or .
What it is: Originally developed by Mobipocket based on an open eBook standard that facilitates hassle-free eBook publishing. It was also the dominant file format for Kindles till December 2023, over a year after they started their Send to Kindle service in August 2022.
What it’s best for: Users of older Kindle generations.
Key benefit: Before it was completely phased out of use, MOBI’s main benefit was its native compatibility with Kindles. It also supports reflowable text, annotations, bookmarks, complex layouts and DRM.
Quick note: You can still transfer MOBI files to Kindles through USB, but only for personal use.
Limitation: You can no longer upload new MOBI files to newer Kindles. However, if your Kindle already had some MOBI files, they remain unaffected.
If you still want to use the MOBI format, companies offering eBook formatting services recommend this if you are targeting mainly on audiences using smaller screens as the image size can’t exceed 64K. With larger devices, the images may appear weird.
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Kindle Formats (Amazon)
File Extension: .azw, .azw3 or .kf8, .kfx
Image Support: Available
Audio Support: Available
Video Support: Available
DRM Support: Yes
What it is: They are various proprietary formats by Amazon created specifically for Kindle devices. AZW is the oldest Kindle eBook format still supported for some users. AZW3 (KF8) and KFX are newer eBook formats by Amazon.
What it’s best for: Kindle devices and ecosystem.
Key benefit: It supports DRM, annotations and advanced formatting. KFX specifically includes features like Amazon’s Enhanced Typesetting and advanced typography.
Limitation: Can only be used on Kindles and are not readable on other platforms without conversion into EPUB or other formats.
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PDF (Portable Document Format)
File Extension: .pdf
Image Support: Available
Audio Support: Available
Video Support: Available
DRM Support: Yes
What it is: Adobe’s Portable Document Format (PDF) is one of the most common eBook file formats for documents that need fixed layouts.
What it’s best for: Textbooks, manuals and design-heavy books.
Key benefit: It preserves the formatting of the content across all devices and screen sizes or orientations. It is also compatible with multiple devices.
Limitation: It doesn’t adapt to small screens and are usually scaled for letter or A4 size sheets. The files sizes can also be large.
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ODF
File Extension: .doc, .xls
Image Support: Available
Audio Support: Available
Video Support: Available
DRM Support: Yes
What it is: The Open Document Format is an open-source, XML-based file format used mostly by LibreOffice and OpenOffice for office documents like text files, spreadsheets, drawings and presentations.
What it’s best for: Open-source publishing workflows, those who want long-term (vendor-independent) access to the files and people with vision impairments.
Key benefit: It is an open standard format with solid cross-platform support, which means that ODF files can be loaded, edited and saved on almost any software or operating system. There is almost no formatting issue or dependency on proprietary licenses.
Limitation: It is not natively supported by most of the e-readers.
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Rich Text Format
File Extension: .rtf
Image Support: Available
Audio Support: Available
Video Support: Available
DRM Support: Yes
What it is: Created by Microsoft, the Rich Text Format is for text sharing across platforms. It was created mainly for sharing and saving documents.
What it’s best for: Simple eBooks that don’t have advanced or complicated formatting.
Key benefit: It allows easy editing, sharing and viewing across different platforms and applications while also preserving the intended look.
Limitation: Apart from images and some graphics, it doesn’t support multimedia and modern eBook features.
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DjVu
File Extension: .djvu
Image Support: Available
Audio Support: Available
Video Support: Available
DRM Support: No
What it is: It is a format designed for scanned documents with high compression. It has advanced compressors that are optimized for low-color images, like text documents.
What it’s best for: It’s the perfect format for image-heavy books, academic papers and historical archives.
Key benefit: You can have small file sizes with good quality as it allows high-resolution scans (300 to 400 DPI) that is good for on-screen reading, printing and storing.
Limitation: It has limited e-reader support compared to PDFs.
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Doc
File Extension: .doc
Image Support: Available
Audio Support: Available
Video Support: Available
DRM Support: No
What it is: DOC is an older Microsoft Word document format made for storing text documents with different formatting options, images and other elements.
What it’s best for: Creating drafts and manuscripts before conversion.
Key benefit: It is to edit, reflow, convert and is widely supported.
Limitation: It has been replaced by the newer format .docx (although it can still be used) and it is not designed as a publishing-ready format. It is also only supported on a select few eBook readers.
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IBA
File Extension: .iba
Image Support: Available
Audio Support: Available
Video Support: Available
DRM Support: Yes
What it is: IBA is Apple Inc.’s proprietary format from iBooks Author (now integrated into Pages) and is based on the EPUB format. Authors can use it for free but they cannot re-purpose the content in other eBook formats to be sold outside the Apple Book Store (formerly the iBook Store).
What it’s best for: Interactive eBooks with multimedia and custom widgets.
Key benefit: It supports animations, videos, interactive quizzes, audio and images.
Limitation: It is compatible only with Apple devices and the Apple Books app so distribution is limited.
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TomeRaider
File Extension: .tr2 or .tr3
Image Support: Available
Audio Support: Not available
Video Support: Not available
DRM Support: Yes
What it is: It is a proprietary eBook format used by the TomeRaider software for storing large collections of text (Wikipedia for example). It is also available in various versions for Windows, Windows Mobile, iPhone, Palm, Symbian, etc. It is very niche and is used for reference works and encyclopedias.
What it’s best for: Specialist collections and reference materials.
Key benefit: It has quick search capabilities and navigation features.
Limitation: It’s features may vary from platform to platform. Also, it is obsolete and rarely used today.
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Comic Book Archive
File Extension: .cba, .cbr, .cbt, .cbz, .cb7
Image Support: Available
Audio Support: Not available
Video Support: Not available
DRM Support: N/A
What it is: It is also called sequential image file and is a type of archive file for sequential viewing of images (mostly for comic books). It is not a distinct file format but a filename extension naming convention and each filename extension indicated what archive type is used. For example, .cba extension will have archive type ACE, .cbr will have RAR [2], .cbt will have TAR, .cbz will have ZIP [3], and .cb7 will have 7z respectively.
Files within the archive are typically in PNG (lossless compression) and JPEG and occasionally you also see BMP, GIF and TIFF files.
What it’s best for: Digital comics and graphic novels. It allows various dedicated functions for readers to go one page forward/backwards, go to first/last page, zoom or print.
Key benefit: Preserves artwork in high quality.
Limitation: There is no reflowable text as it is purely image-based.
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DOCX
File Extension: .docx
Image Support: Available
Audio Support: Available
Video Support: Available
DRM Support: N/A
What it is: It is the newer, modern XML-based Microsoft Word format popularly used for text documents.
What it’s best for: Preparing manuscripts before exporting to EPUB or PDF.
Key benefit: It supports rich formatting, easy editing, reflowing and collaboration.
Limitation: It must be converted into a proper eBook format before distribution and is supported only on a few eBook readers.
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FictionBook
File Extension: .fb2
Image Support: Available
Audio Support: Not available
Video Support: N/A
DRM Support: No
What it is: It is a Russian XML-based eBook format that is popular in Russia and Eastern Europe. It is designed to contain the entire book content, that includes text, images, metadata etc.
What it’s best for: Literature and novels in specific regions.
Key benefit: It has structured metadata and is lightweight. The .fb2 focuses on the books structure and not the precise visual appearance. So, it allows dynamic text wrapping and seamless layout adjustments across various devices.
Limitation: There is limited global adoption for the .fb2 file format.
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PostScript
File Extension: .ps
Image Support: Available
Audio Support: Not available
Video Support: Not available
DRM Support: No
What it is: PostScript is a page description language developed by Adobe and is a precursor to the PDF. It defines how text, graphics and images should appear on a page and it is mainly used for high-quality printing and desktop publishing.
What it’s best for: Print-ready files and technical publishing.
Key benefit: It allows for precise layout control. PostScript can also incorporate bitmap graphics and text, so it is a versatile tool for graphic design and publishing workflows.
Limitation: It is outdated and most publishers today prefer to work with PDF.
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HTML (Hypertext Markup Language)
File Extension: .html, .htm
Image Support: Available
Audio Support: Available
Video Support: Available
DRM Support: No
What it is: It is mostly known for web pages but it also serves as a core component for many popular eBook formats. Basically speaking, it is an eBook format that uses Hypertext Markup Language (HTML) as its foundational structure for content and presentation. It is the web standard for digital content.
What it’s best for: Web-based eBooks, tutorials and online publications.
Key benefit: Flexible, supports multimedia and hyperlinks.
Limitation: It needs a browser or web reader and is not optimized for offline e-readers.
eBook File Format Comparison
| Format | Pros | Cons | Best For |
|---|---|---|---|
| EPUB | Universal, reflowable, multimedia | Older Kindles lack support | Most readers & publishers |
| MOBI | Legacy Kindle use | Outdated, phased out | Old Kindle users |
| AZW, AZW3/KF8, KFX | DRM, advanced formatting | Kindle-only | Kindle ecosystem |
| Fixed layout, print fidelity | Poor on mobiles | Textbooks, manuals | |
| IBA | Interactive, multimedia | Weak device support | Open-source workflows |
| RTF | Cross-platform | Lacks features | Basic text eBooks |
| DjVu | High compression | Limited support | Image-heavy works |
| DOC/DOCX | Editable, rich formatting | Not distribution-ready | Draft manuscripts |
| TomeRaider | Fast search | Obsolete | Reference collections |
| Comic Archive | Preserves comics | No reflowable text | Graphic novels |
| FictionBook | Lightweight, XML-based | Regional | Novels (Eastern Europe) |
| PostScript | Print-ready | Outdated | Technical publishing |
| HTML | Multimedia, web-ready | Needs browser | Online eBooks |
If you want to choose the eBook formats depending on the device compatibility, then for Android, Sony Readers, Nook, Nook Color, and Nook Tablet, EPUB is the best. For PC, Mac, iPhone, iPad, and iPod Touch, choose PDF or EPUB format. And, when it comes to Kindle and Kindle fire devices, MOBI or PDF is the best.
Conclusion
Always keep in mind that choosing the right file format for your eBook readers comparison is a crucial step in not just making your eBook successful but also in reaching a wide range of audiences. You may be looking for the best ebook formats for Kindle or any other device, however, having comprehensive knowledge on the different types of eBook formats will help you to choose the correct format that can seamlessly serve your purpose. So, take the time to collect all the desired information to narrow down the best option for your project needs.
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