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Difference Between EPUB, PDF, MOBI and AZW E-Book Standards

Difference between various e-book formats like EPUB, Mobi, PDF and AZW.
Samyak Lalit | March 24, 2015 (Last update: April 24, 2021)

Samyak Lalit is an Indian author and disability rights activist. He is the principal author and founder of projects like TechWelkin, WeCapable, Viklangta, Kavita Kosh among many others.

I work for a big publisher who recently decided to release e-book editions of their thousands of unique book titles. At that time I researched about the difference between various e-book formats like EPUB, AZW, MOBI and PDF.

People often ask what is the difference between an e-book and a PDF file? Well, I must say that it is indeed pretty frequently asked question. An e-book and a plain PDF file are not very different from each other —but if you go in finer details, the differences will appear. I will explain this difference towards the end of this article. Today let’s understand the difference among EPUB, AZW, MOBI and PDF eBook formats.

What is an eBook?

Let’s begin with understanding the basic question, what is an e-book? An e-book is essentially an electronic document. In simple terms, it is just a computer file. In modern terminology, electronic book or e-book is the electronic version of a printed book. Electronic book can be read using computer or a custom designed mobile device.

Difference between various e-book formats like EPUB, Mobi, PDF and AZW.

Difference between various e-book formats like EPUB, Mobi, PDF and AZW.

In last one decade, the Internet and electronic gadgets have spread like wildfire all over the world. With this, the habit of reading books on digital devices has also grown. People have accepted e-books. Major Internet companies like Amazon quickly jumped onto this opportunity and developed specialized devices for e-book reading.

A number of e-book standard formats have been developed in order to make e-books compatible with the device specific features.

MOBI E-book Format

Mobipocket (often called just mobi) is an e-book standard format. It was initially launched by Mobipocket SA, a French company, in the year March 2000.

Mobipocket is a free e-book reader software. In 2005, Amazon acquired Mobipocket. E-books created using Mobipocket standard carry .prc or .mobi extensions. In the foundation of this standard is the Open eBook standard. Mobi format uses XHTML, JavaScript and can also include frames.

Mobi e-books can be read using Mobipocket e-book reader. This reader is actually a software and it can be installed on a large number of mobile operating systems and devices like smartphones and PDAs.

AZW E-book Format

When Amazon developed Kindle, its popular e-book reading device, it needed an e-book standard for Kindle. As I told you, Amazon had bought Mobipocket in 2005. So, Amazon modified the MOBI format a little bit and came up with the AZW e-book format.

The primary difference between MOBI and AZW is that AZW uses asterisk instead of dollar sign in the serial number scheme. Also, unlike the original MOBI format, the AZW format does not allow the use of JavaScript.

E-books with extension .prc are fully compatible with the Kindle devices and can be directly read on it.

AZW e-book format is used only on Kindle devices. Kindle does not support EPUB e-book format. But now that EPUB e-book format is also becoming a sort of industry standard, Amazon has released KindleGen software, which can convert .epub e-book into .mobi e-books.

AZW3 or KF8 E-book Formats

Early Kindle devices used AZW e-book format, which was a modified MOBI standard. But as Amazon developed even better versions of Kindle, the AZW e-book format also evolved with time.

AZW3 or KF8 is the e-book format for the fourth generation Kindle devices. This format was introduced when Amazon released Kindle Fire in the market. KF8 stands for Kindle Format 8.

AZW3 is a proprietary format of Amazon. It can not be used by any other company.

AZW3 is a Digital Rights Management (DRM) restricted format. It means that the AZW e-book files are locked to a particular device. These files can not be transferred to another device. This is done to put a stop on piracy.

PDF E-book Format

Adobe Systems developed Portable Document Format (PDF) format in 1993. This is one of the best known e-book formats as it has been there since long. PDF format is so popular that that PDF e-book files are supported by almost all e-book readers.

In 2001, Adobe made the PDF format open source.

Original PDF standard did not support reflow feature. But in 2012, an updated format called PDF/UA was released with reflow features. PDF/UA got only moderate support from the third party hardware and software manufacturers.

Difference between PDF and E-book

As we all have been seeing PDF files since we have learnt to use computers, a large number of people feel that a PDF file is an e-book. But when they see so much talk about e-books they begin to feel that an e-book must be something more sophisticated than a simple PDF file!

Well, actually a PDF file is indeed an e-book. But the modern and popular e-book formats have more features than the plain original PDF. One of such features is reflow. E-book formats like EPUB, MOBI and AZW, support reflow of the book. Reflow means that the same e-book can be read on devices of different dimensions. E-book will automatically adjust the content according to the screen size. Most of the PDFs are not designed to be reflowable. That is one of the major difference between an E-book and a PDF file.

Another big difference is that the original plain PDF format did not have the embedded meta information. Whereas E-books contain hidden meta information about the book itself and about the author, publisher etc.

You can convert any file into a PDF file but to make it a proper e-book, this PDF file should contain all the required meta information. This meta information is required to identify the book and to know about its various properties.

Encryption is yet another aspect that makes a proper e-book different from a plain PDF file. E-books may or may not contain encryption and security measures to allow only the authorized people to read them. Plain PDF files often lack such a security.

EPUB E-Book Format

EPUB is an open standard format for e-book publishing. It was created by the International Digital Publishing Forum (IDPF). Unlike Amazon’s MOBI and AZW formats, EPUB is a public and open standard.

EPUB is supported by a large number of vendors. EPUB can be read by Apple’s iBooks app (iOS), BlackBerry devices, Kobo eReader, Google Books app (Android) and almost all other notable e-book readers.

Only Amazon’s Kindle does not support EPUB. Amazon prefers to use its proprietary AZW format. In fact, as I said before, Amazon’s KindleGen can convert .epub format into .mobi format. So, if you have an e-book created with EPUB format, you can easily convert it into .mobi format and read it on your Kindle device.


Need of having defined formats for e-books was recognized as early as in mid 1990s. Adobe and Amazon have been the front-runners in the race of getting e-book market share. Kindle devices, however, make Amazon the undisputed leader in the e-book industry. MOBI and AZW e-book formats are proprietary and Amazon is using them to strengthen its position in the e-book industry. Widespread use of the open EPUB e-book format has, however, dented the Amazon’s monopoly. In my view, it is important to further develop EPUB. Also more and more vendors should provide support for EPUB e-books.

I hope it was useful for you to know the difference between EPUB, PDF, MOBI and AZW E-book standards. In case you have any questions, please feel free to ask. I will try my best to help you. Thank you for using TechWelkin!


9 responses to “Difference Between EPUB, PDF, MOBI and AZW E-Book Standards”

  1. Irving M says:

    Thanks, I really need this information.

  2. Sekar says:

    Hi Sir,
    I am Sekar having 7+ years of eBook Conversion projects experience and knowledge in e-publishing industry. Currently I am working as a freelancer for many reputed concern. I can provide the services like epub2, epub3, Fixed Layout, Mobi and XML projects in best quality and on time delivery of projects.
    To build your trust on me, you can send me some sample files, so that I will prove my quality on files and you can validate it before moving into live projects.

  3. Chandima says:

    1.I wrote 6 Psychological Counselling books and 3 Buddhism books in Sinhala language. I’m a Sri lankan. Can I write ebooks in Sinhala?

    2. I like creating positive posts for fb. (sinhala). Can I earn money from this way?

    • Lalit Kumar says:

      If you can write printed books — yes, for sure, you can author ebooks as well! As for making money through FB, you have to have a lot of (i mean hundreds of thousands of) followers on FB.

  4. Rahul Vithlani says:

    What are the primary differences between epub and mobi formats ?
    What are their pros and cons ?

  5. Kam says:

    If I’m self-publishing an e-book and I’m planning to publish only on Amazon, then should I use epub or mobi?

    • Lalit Kumar says:

      It rally doesn’t matter much. But if you are targeting specifically the Amazon Kindle platform, then nit is better to go for mobi or azw3.

  6. Ramesh Kanwal says:

    I got enlightened and enriched. thanks

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