I want to publish my first e-book, but the multitude of available file formats (PDF, ePUB, MOBI, TXT, etc.) is a bit overwhelming. As a result, I am not really sure which format (if any) would be able to reach most readers.

Before I opt-in to simply offering multiple file formats (and let individual readers choose what fits their needs best), I would like to know if there is any "one-file-format-fits-all-ebook-readers" file format.

Does any "universally agreed-upon standard file format" for ebooks exist, that most (if not all) ebook readers are able to handle?


Virtually all e-book readers can display PDF files. Unfortunately, PDF documents are "pre-rendered" - the text is positioned on the page in absolute coordinates and text cannot reflow on smaller / larger devices (without hacks or trickery that rarely work well).

TXT files are a good option if formatting isn't a concern. Most e-book readers can display TXT files (I just double-checked that they work out-of-the-box on my Kindle Touch). The downside, of course, is that you cannot use any formatting.

This leaves you with two common formats:

  • EPUB (supported by Nooks, iBooks, Kobo, and Sony devices)
  • MOBI (supported by Kindle devices)

This page displays a table of devices and their supported formats.

I would actually suggest a completely different approach - produce content using a markup language (like Markdown or HTML) and then use a tool to convert the files to the e-book formats you wish to support. Tools like Calibre support nearly every format under the sun, so you can choose as many formats as you want.

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    Yup. Have your master copy in a markup language, and then convert from there into any format you need. It's the simplest and most reliable. – Standback Dec 19 '13 at 8:45
  • Also many distribution networks would only accept PDF and or ePub versions these days. Also if you do decide to write the eBook in markup language first, make sure you conform to the correct ePub version, ePub 2.1, ePub 3, Enhanced ePubs etc. – Phillip Morton Dec 19 '13 at 9:04
  • +1 for mentioning Calibre - the best book reader/library management out there. – Dzhuneyt Dec 19 '13 at 10:08
  • Tongue-in-cheek: if you can live without checks from Amazon, don't do MOBI at all (helps breaking Amazon's lock-in strategy and freeing people from them, if only a little). – Raphael Feb 7 '14 at 11:12
  • As a former author who published via Amazon I can't agree more with using a Markdown language. I started with their specs for doing a DOC format I think, and it was a nightmare. That's why I wrote a Perl program to convert MultiMarkdown to EPUB. It's easy to learn and the EPUB passes validation. And it's free. Markdown, in general, is much easier to see your text, than compared to HTML. HTML, while not that hard to learn, is just visually messy and distracting. Markdown much less so. PM me if you want more info. I ran out of spa – Bulrush Apr 18 '16 at 12:46

Apart from the consideration what format the most people have, you should consider your wish to control over the layout of the text and how well the format can be converted to other formats by your readers.

Some formats like TXT allow very little control over the layout. In PDF you have much control over the layout, as you have in EPUB and MOBI.

Conversion of some formats is easier than others, the calibre FAQ gives a list of best formats to convert in decreasing preference: LIT, MOBI, AZW, EPUB, AZW3, FB2, DOCX, HTML, PRC, ODT, RTF, PDB, TXT, PDF. So if you would provide only PDF and TXT readers cannot easily provide good readable EPUBs for their device. In my experience the difference between the first 5 formats for input is minimal.

That leads me to recommend EPUB or MOBI as the formats if you target only EBooks and one of those and TXT if you want to capture the computer audience as well, but don't care about layout. Replace TXT with PDF (combined with EPUB or MOBI) if you care about the layout.

And then of course the software you use to generate the format has some influence on what you can do, but I assumed that you can generate the formats you indicated in your question in some way.


Most people here are focusing on the device side of the question, but there's another one that may be equally important: the economic side. This depends on what your goal with your book is—are you planning to sell it, or do you just want to distribute it so that lots of people can read it? If the latter, then yes, text files or PDF are reasonable options (though bear in mind that PDFs by and large are not reflowable, which means that they can be hard to read on devices with small screens, like cell phones).

If you're intending to sell your book, then you need to take into account the policies of the ebook marketplaces you're interested in selling through. The major market out there is, of course, Amazon, and they only sell MOBI/KF8 formats. Barnes & Noble, iBooks, Google Play, and Kobo all sell EPUB files, but even taken all together, Amazon is the larger market. The good news, though, is that in order to create a mobi file, you need a valid EPUB file and Kindle Previewer, so EPUB will pretty much get you a MOBI/KF8 file as well.

EPUB files are essentially just zipped up collections of HTML pages, so if you're looking for a single-source format, XHTML would be a great choice. Ensuring that it's the more-rigid XHTML will allow for greater transformability of your files, meaning that in the future it will be much easier to run your file through an automated tool that will convert it to whatever the Google Glass ebook format (or whatever) is.

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    "Most people here are focusing on the device side of the question…" Well, I guess that's because I asked "…that most (if not all) ebook readers are able to handle?" Here, "ebook readers" clearly points at the devices, not the human readers who use those devices to read their ebooks. ;) - Thanks for your answer nevertheless. Btw.: I use Latex for my purposes. Things like XHTML quickly tend to become less handy when it comes to transforming into several formats. – e-sushi Feb 4 '14 at 18:30
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    Fair enough! I was focusing more on the "As a result, I am not really sure which format (if any) would be able to reach most readers," which to me implies that you're looking to distribute the book to a large number of readers. Good luck with your endeavors, and I hope some of my info is useful! – Tom Feb 4 '14 at 18:34

There is no universal one-size-fits-all, but I would say that a PDF file would be one that most ereaders can handle, but you never know.

I would publish a EPUB version and a PDF version just for the convenience of your readers.

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    True, but PDF is also the one non-customizable, reflowable-with-difficulty, unwieldy-on-small-reaeders, useful-at-most-for-printing format I'd studiously avoid. – DaG Dec 19 '13 at 8:31

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