General eBook Formats in 2020

There are dozens of eBook formats in the digital book market. What ebook format have you ever seen? Epub, PDF, CRB, Kindle and more.  But do you really know them? Here I will share the common ebook formats that ebooks are using to help you get the basic knowledge of ebook formats.

Epub	Portable Document Format(PDF)	Kindle
iBook (Apple)	CDisplay Archived Comic Book format	DAISY
Djvu	Microsoft LIT	Microsoft Word
Plain Text Files	FictionBook (fb2)	Rich Text Format

Epub

File Extension: .epub

Epub, short for electronical publication, is a technical standard for e-books created by the International Digital Publishing Forum(IDPF).

EPUB files can store words, images, stylesheets, fonts, metadata details, and tables of content. The latest epub version is epub 3.2. It supports the latest versions of HTML, CSS, and SVG, and has built-in support for embedded interactivity, audio, and video. It is also designed in a way that allows the text and images reflow to fit all screen sizes.

That’s no hard to understand that why a majority of eReaders support epub files.  Beyond the eReaders, it can be read on a variety of devices, including computer, smartphones, tablets and most eReaders (except kindle). Nowadays, epub is the most widely supported ebook format.

For most ebook vendors adobe epub format and encrypted epub files with its own DRM, such as adobe adept drm, ibooks drm, nook ebook drm and more.

To remove drm from epub books, free epub drm removal will help you.

Portable Document Format(PDF)

File extension: .pdf

PDF, short for Portable Document Format, is invented by Adobe Company and first released in 1993. PDF format is used when you need to save files that cannot be modified but still need to be easily shared and printed. It can store text, images, multimedia elements, web page links and more. What’s more, PDF adds support for features such as compression, passwords, semantic structures and DRM.

Because the format is designed to reproduce fixed-layout pages, re-flowing text to fit mobile device and e-book reader screens has traditionally been problematic.

PDF file format also supports DRM. That's why almost all ebook vendors adopt PDF to their ebooks, especially etextbook. When PDF encrypted with Kindle DRM, it will become AZW4 format.

Kindle

File extension: mobi(.prc) azw; .azw3 or .kf8; .kfx

Kindle file format is an proprietary ebook format developed by Amazon.com with multiple extensions, such as .azw, .azw3 or .kfx and more.

AZW that is based on Mobipocket; in fourth generation and later Kindles, AZW3, also called KF8; and in seventh generation and later Kindles, KFX.

The Mobipocket format is known as .mobi format. It was the first ebook file format that adopted by Amazon. Actually, it is based on the Open eBook standard using XHTML and also include JavaScript and frames. What’s more it is also supports native SQL queries to be used with embedded databases.

Later Amazon replace the mobi format with .azw format and encrypted the file with Kindle DRM. So we can consider .azw files as the Mobi format with DRM protection that only allows them to be read on Kindles or kindle apps. But AZW files can store complex content like bookmarks, annotations, and highlights. AZW files are only accessible from Amazon online books store.

With the release of the Kindle Fire reader in late 2011, Amazon.com also released Kindle Format 8, also known as .AZW3. The .azw3 file format adds support to a subset of HTML5 and CSS3 features, with some additional nonstandard features which makes it more advanced to support additional styles, fonts and layouts.

Then Kindle kfx format (kf10) is developed, accompanying with the toughest kindle DRM forever. The .KFX format introduces new features like support for soft-hyphens using a new enhanced typesetting engine, a new image file format called JXR, that has a higher compression ratio, and the new Bookerly font which is kindle-exclusive font providing improved readability on digital devices. Just like azw format, Amazon kindle store is the only way to access the kindle kfx format ebooks.

iBook (Apple)

File extension: .ibooks(IBA)

The .ibooks format, known as Multi-touch book, is created with the free iBooks Author ebook layout software. This proprietary format is based on the EPUB standard, with some differences in the CSS tags used in an ibooks format file, this making it incompatible with the EPUB specification.  It can contains a wide variety of interactive elements, which makes them particularly well-suited for textbooks, cookbooks and picture books.

As of July 1, 2020, iBooks Author will no longer be available to new users. iBooks Author can still be used on macOS 10.15 and earlier, but there will be no new updates.

CDisplay Archived Comic Book format

File extension: .cbr (RAR); .cbz (ZIP); .cb7 (7z); .cbt (TAR); .cba (ACE)

CDisplay Archived Comic Books file is a comic book saving multiple images, commonly .PNG, .BMP, .GIF or .JPEG files. All images are stored in a compressed archive format such as RAR, ZP TAR, 7Z or ACE. But they are goes by a different name, like RAR ARCHIVED is CBR, ZIP archived is CBZ. As you can see, the file extension, or more specifically the last letter of the file extension, tells you what format the CDisplay file was compressed with.

The comic files that use the CDisplay Archived Comic Book format—be it CBR, CBZ, CBT, CB7, or CBA—can all be opened using CBR Reader, a free comic book format reader program

DAISY – Digital accessible information system (DAISY)

File extension: .daisy

The Digital Accessible Information SYstem (DAISY) is the emerging world standard for digital talking books for people who are blind or have a print disability.

The current version of DAISY 3.0, was released in mid-2005 and is a complete rewrite of the standard. It was created with the goal of making it much easier to write books complying with it. It's worth noting that DAISY can support plain text only, audio recordings (in PCM Wave or MPEG Layer III format) only, or a combination of text and audio. Specialized software can read these books and allow users to set bookmarks and navigate a book as easily as a sighted person would with a print book.

DAISY is already aligned with the EPUB technical standard, and is expected to fully converge with its forthcoming EPUB3 revision.

Djvu

File extension: DjVu, Djv

DjVu is a compressed image format specialized for storing scanned documents. A DiVu file can contain compressed yet high-quality color images, photographs, text and drawings. It is mostly used by manuals, newspapers, ancient documents, text that has been scanned into a computer. Just like PDF format, DjVu files cannot be re-flowed.

Microsoft LIT

File extension: .Lit

LIT stands for Literature. It is a type of electronic book format created by Microsoft and used solely by the Microsoft Reader program, which was first released in 2000, but discontinued in 2012.

Actually, .lit files are data files rather than documents or media, that makes they are not to be viewed at all. The DRM-protected LIT files are only readable in the proprietary Microsoft Reader program.

Microsoft Word

File extension: DOC, DOCX

DOC and DOCX are document file formats used by Microsoft Word. They are also used with most word processing software, including OpenOffice. Doc and Docx files contains a variety of document content, including text, images, shapes, styles and page formatting.

DOC files use a proprietary binary format and are used by Microsoft Word 2003 and earlier.

The DOCX extension is used by Microsoft Word 2007 and later. The X in DOCX stands for XML standard. DOCX files use a newer file format referred to as Open XML, which stores a document as a collection of separate files and folders in a compressed zip package. This means that you can replace the DOCX extension of the file with .zip and still open the documents with any zip compression software.

Plain Text Files

File extension: .txt

The plain text file is the most common-used ebook format, ending with extension .txt. Almost all operating systems can read ASCII text files. Since it is using the simplest ebook encoding, formatting (changing fonts or font styles), images and graphic are not supported. It also doesn’t have the fixed layouts, DRM protection or interactivity. TXT formats are great for text-heavy ebooks, like online novel.

FictionBook (fb2)

File extension: .fb2

An FB2 file is an FictionBook 2.0 file that contains the structure of the ebook. It is based on XML format and contains special tags for describing each element of the book. Instead of specifying its appearance, it focuses more on describing the structure of the file. The .fb2 file includes all the ebook metadata, such as as the author name, title, and publisher. Hence the format is convenient for automatic processing, indexing, and ebook collection management.

Rich Text Format

File extension: .rtf

RTF, short for Rich Text Format, is a document file format that used by Microsoft products. It was first released by Microsoft in 1987 for cross-platform document interchange. That means if you create one RTF file on Windows, you’ll be able to send it to your friends who uses Mac or Linux. It is also user in other type of apps, such as email clients.

What’s more, RTF file can be easily reflowed, edited, and converted to other ebook format.

I've already introduced the most common-used ebook format nowadays. Hope the knowledge I shared here will be helpful when you come across these ebook formats during your reading.

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