Answers.Body: <p>First, a note: I will not be considering PDFs in this answer, because I do not consider PDFs to be ebooks. There are a number of reasons for this, like lack of reflowability and end-user customization options, but the primary reason is that PDFs are not generally sold at sites that sell ebooks--you can't sell your PDFs through iBooks or the Kindle store or whatnot. Others have other opinions, and that's fine&mdash;the relevant info is that I won't be considering PDFs here.</p>
  
  <p>In terms of variety of devices supporting the format, epub is the clear standard&mdash;it's supported on nearly everything that reads ebooks. When you look at numbers, though, it's a different story: according to <a href="http://www.digitalbookworld.com/2013/bisg-report-a-few-more-ebook-stats/">an article</a> at Digital Book World, a recent Book Industry Study Group found the following statistics to the question "Where do you typically acquire ebooks?":</p>
  
  <pre><code>Amazon.com website: 51.3%
  Amazon App: 15.7%
  iBooks/iTunes (Apple): 8.2%
  Barnes &amp; Noble App: 6.1%
  Barnes &amp; Noble website: 5.7%
  All other sources: 12.8%
  </code></pre>
  
  <p>This means that Amazon accounts for roughly 2/3 of the sales of ebooks, making their proprietary mobi/KF8 format the dominant format.</p>
  
  <p>In essence, there is no "winner" yet, and there is not likely to be any time soon. Apple, Google, Barnes &amp; Noble, and Kobo are enough to ensure that epub will remain alive and kicking for quite some time. With a majority of the sales, Amazon has no impetus to switch to a standard, and they don't appear to be in any danger of losing much market share. Where we are is where we're likely to be for quite a while, which means making two formats: epub and mobi/KF8. fortunately, Amazon has gotten much better at making tools that convert from epub to their format, so concentrating on epub will give you something for Amazon as well with little extra work.</p>
  
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2014-08-24T12:51:44.460Z
Answers.Text: Thanks, this is a good starting point (!)... But it is incomplete without public domain content, and without non-USA e-commerce statistics. Example: [As of March 2014, Project Gutenberg claimed over 45,000 items in its collection](https://en.wikipedia.org/wiki/Project_Gutenberg) (but [not have any format-download statiscs](http://www.gutenberg.org/wiki/Gutenberg:Readers'_FAQ#R.9._I_searched_for_a_book_I_know_is_in_Project_Gutenberg.2C_but_got_no_results.)); [SciELO](http://books.scielo.org/) and many other minor public domain e-book projects are also distributing ebooks.
Answers.UserDisplayName: Peter Krauss
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2014-08-24T12:58:58.217Z
Answers.Text: Another non-usual but growing source of e-books are  scientific articles: [PubMed Central](https://en.wikipedia.org/wiki/PubMed_Central) have 3.1 MILLION Articles that now (2014) are ditributed also in EPUB format.
Answers.UserDisplayName: Peter Krauss
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2014-08-24T19:43:54.617Z
Answers.Text: How about software support? As I read around, epub seems to be a much more popular format to create books (even if Kindle coverts it to mobi).
Answers.UserDisplayName: Greg
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2014-08-24T20:33:13.317Z
Answers.Text: Epub is a much more popular way to create ebooks because Amazon's format is proprietary; you can't directly make it. You can only convert to it from epub or a few other formats.
Answers.UserDisplayName: Tom
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2014-08-27T03:51:36.727Z
Answers.Text: @Tom That would be sad if the dominant format would be something that needs another even just for creation. Even PDF is more open in that sense.
Answers.UserDisplayName: Greg
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2014-08-27T07:52:17.580Z
Answers.Text: @greg: 1000% agreed; that's why I don't ever buy books from Amazon. They're proprietary and terrible.
Answers.UserDisplayName: Tom
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2014-09-07T16:59:41.737Z
Answers.Text: @Tom they are easily converted from Kindle format to epub by programs like calibre
Answers.UserDisplayName: mmmmmm
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2014-09-07T17:02:34.077Z
Answers.Text: Sure, but given the option, why support a company that does stuff I don't approve of?
Answers.UserDisplayName: Tom
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2014-09-16T00:55:35.747Z
Answers.Text: Public domain content is not really relevant. Almost all such content will be initially EPUB, but EPUB to MOBI and MOBI to EPUB are so trivial, that until Amazon finally kills off all competition, everything available in MOBI/AZW/KF8 will be available in EPUB and vice versa (in fact, I downloaded the same book from Amazon as AZW3 and Kobo as EPUB this week).
Answers.UserDisplayName: Auspex
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2016-05-22T20:59:40.847Z
Answers.Text: Hi, perhaps some news: [do you know this estimates](https://fortunedotcom.files.wordpress.com/2015/09/2015-aug-trend-units.png)? They are come from [this article](http://fortune.com/2015/09/24/ebook-sales/).
Answers.UserDisplayName: Peter Krauss
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2021-02-05T10:43:31.967Z
Answers.Text: Hi, come 2020 news about the theme, new statistics?    PS: for my last comment, correcting [2015 chart estimatives link](https://content.fortune.com/wp-content/uploads/2015/09/aap-unit-sales.png).
Answers.UserDisplayName: Peter Krauss
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2014-08-24T01:21:36.747Z
Answers.LastActivityDate: 2014-08-24T01:21:36.747Z
Answers.UserDisplayName: Tom
Answers.Body: <p>Amazon has over 2.8 million ebooks, including nearly all public domain books. See the left hand column, which provides an update to date count of ebooks available: <a href="http://www.amazon.com/s/ref=lp_154606011_ex_n_1?rh=n%3A133140011&amp;bbn=133140011&amp;ie=UTF8&amp;qid=1410374478" rel="nofollow">http://www.amazon.com/s/ref=lp_154606011_ex_n_1?rh=n%3A133140011&amp;bbn=133140011&amp;ie=UTF8&amp;qid=1410374478</a></p>
  
  <p>This 2.8 million books makes things like Project Gutenberg statistically insignificant.</p>
  
  <p>Your quote that "EPUB format is the most widely supported vendor-independent XML-based" is obviously designed to exclude MOBI/Kindle from the mix, because it's not vendor-independent. And sure, outside of Amazon, it is the dominant standard.</p>
  
  <p>But more importantly, why do you want to know?</p>
  
  <p>If the answer is because you want to know what format to publish a book in, versus you want to build an eReader app, versus you're writing a research paper, there are very different implications.</p>
  
  <p>If you're an author publishing commercial fiction, since <a href="http://www.forbes.com/sites/jeffbercovici/2014/02/10/amazon-vs-book-publishers-by-the-numbers/" rel="nofollow">Amazon has about 65% of the ebook market</a>, you must publish in MOBI to be successful. If you are an indie author, Amazon has an even bigger percentage of the market for indie authors (anecdotally 80+%), and so it becomes even more crucial.</p>
  
  <p>If you are providing an ebook where access is crucial, e.g. a school text book that must be available to all students, then you must publish in both EPUB and MOBI. </p>
  
  <p>Since EPUB and MOBI can be easily converted back and forth, one might argue that the question is irrelevant. Simply provide books in both formats.</p>
  
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2014-09-11T00:38:05.350Z
Answers.Text: Hum... a first point... I not  know how write right English  (I need help of web-translators), but *"my book" can add "+1" at Kindle Store counter*... By other hand, "my book" will never appear on Project Gutenberg. When we count "any thing" at Amazon we need to compare it with "any thing" at the *full-Internet*, not only with Gutenberg...
Answers.UserDisplayName: Peter Krauss
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2014-09-11T14:05:08.290Z
Answers.Text: You cited discussions, not reliable sources of statistics... Forbes, that cite Newyorker.com, are good sources, but there are no newer result for @Tom's answer (your 65% is the "51.3%+15.7%" of Tom's). The BISG (Book Industry Study Group cited by Tom) report is good, so what is wrong or what is what's missing? BISG is an U.S. trade association, as Amazon; and Amazon, with others, *with focus on non-public contents*, was pay BISG to produce the report... Some good results found there, and perhaps other independent report confirm the same results... So, where the "other independent reports"?
Answers.UserDisplayName: Peter Krauss
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2014-09-11T23:19:26.760Z
Answers.Text: Again, I will refer back to: What decision are you trying to make? What is the purpose of the question? Are you testifying in front of a judge? That requires a different level of reliability than say, trying to decide how and where to publish your novel.
Answers.UserDisplayName: William Hertling
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2014-09-12T00:38:15.003Z
Answers.Text: We develop software and offer services for "content management/styling/transform"... Some software need a 2-year plan... What will the scenery in 2 years? How will the market and the "reading habits"? Our main customers are  public domain content producers, for non-US readers... This is our reality, and is the same for many middle/small company around non-US-world.
Answers.UserDisplayName: Peter Krauss
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2014-09-16T00:58:54.917Z
Answers.Text: If that's your need, then it's a complete non-issue. Decide on a base platform (and personally, I think EPUB is the one to use) and then convert to the other for distribution to nearly 100% of the market.
Answers.UserDisplayName: Auspex
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2016-05-22T20:59:57.863Z
Answers.Text: Hi, perhaps some news: [do you know this estimates](https://fortunedotcom.files.wordpress.com/2015/09/2015-aug-trend-units.png)? They are come from [this article](http://fortune.com/2015/09/24/ebook-sales/).
Answers.UserDisplayName: Peter Krauss
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2014-09-10T18:49:32.263Z
Answers.LastActivityDate: 2014-09-10T18:49:32.263Z
Answers.UserDisplayName: William Hertling
Answers.Body: <p>   <strong>This is a Wiki, please edit and collabore!</strong> We need good English and updated content.</p>
  <h2>Concepts</h2>
  <p>As used here:</p>
  <ul>
  <li><p><em>e-book</em> and <em>e-book reader</em>: <a href="http://en.wikipedia.org/wiki/E-book" rel="nofollow noreferrer">e-book</a> is the content, a file; and the <em>e-reader</em> is the device, a hardware (or software+hardware). Sometimes the content (e.g. CSS or Javascript code)  have some algorithmic prescriptions for e-reader.</p>
  <ul>
  <li><em>e-reader</em>: considering here that an e-reader is a &quot;<a href="http://www.ecolibris.net/ebooks.asp" rel="nofollow noreferrer">paper substitute</a>&quot; device, so a Desktop PC computer or an iPhone are not dedicated e-readers, but Kindle and a <a href="http://en.wikipedia.org/wiki/Tablet_computer" rel="nofollow noreferrer">Tablet computer</a> are.</li>
  </ul>
  </li>
  <li><p>&quot;<em>usable e-book format</em>&quot;: in a broader sense, paper-oriented formats, like <em><a href="http://en.wikipedia.org/wiki/PostScript" rel="nofollow noreferrer">PostScript</a></em> or <em><a href="http://en.wikipedia.org/wiki/Portable_Document_Format" rel="nofollow noreferrer">PDF</a></em>, are acceptable for e-books, and can be called <em>e-book formats</em>.</p>
  </li>
  <li><p>real, strict sense <strong>e-book format</strong>: neither a &quot;web format&quot;, like HTML, nor a &quot;paper format&quot;, like PDF. The e-Books are &quot;<a href="http://www.w3.org/TR/css3-page/" rel="nofollow noreferrer">paged media</a>&quot;, as paper books, but with diagramming flexibility: an e-book need to be <a href="http://en.wikipedia.org/wiki/Reflowable_document" rel="nofollow noreferrer">reflowable</a>, a resizable content that adapts to different resolutions and different <a href="http://en.wikipedia.org/wiki/Aspect_ratio_(image)" rel="nofollow noreferrer">aspect-radio screens</a>. <br>PS: generic HTML is not an ebook format because is not &quot;all in only one file&quot;, but sometimes (e.g. using inline SVG and base64-encoded PNG images) HTML can be adapted for it.</p>
  </li>
  <li><p>&quot;interactive e-book format&quot;: another growing demand for e-books are interactivity (<a href="http://www.youtube.com/watch?v=nuHuotsUxyE" rel="nofollow noreferrer">EPUB example</a> ), but we can ignore this demand here, in favor of the strict sense, and the necessity of <a href="http://www.gutenberg.org/" rel="nofollow noreferrer">classic books</a> into digital devices.</p>
  </li>
  </ul>
  <p>So, conceptually, PDF is considered an (usable) <em>e-book format</em> because it is a legacy from old paper-oriented systems, where authors and layout designers were oriented to the paper size. As of 2012 the screen of the &quot;e-book reader&quot; is the final recipient of the content, and layout authoring is oriented to (some) screen adaptability.</p>
  <p>There are three important criteria — metrics to check if a format is <em>de facto</em> standard — for electing e-book format popularity:</p>
  <ul>
  <li><p>most widely <strong>supported formats</strong>: between popular e-book readers, statistics about direct support (without content loss or conversion demand) for each format.</p>
  </li>
  <li><p>more <strong>downloads</strong>: sales and download counting, in reliable &quot;sales statistics&quot; at bookstores and download statistics at libraries.</p>
  </li>
  <li><p><strong>availability</strong>: number of distinct online links (at online libraries and others), each link to a distinct file download of a public domain e-book. Example: number of titles into the <a href="http://www.gutenberg.org/" rel="nofollow noreferrer">Project</a>, <a href="http://www.scielo.org/" rel="nofollow noreferrer">SciELO</a>, etc.</p>
  </li>
  </ul>
  <h2>New results in 2020?</h2>
  <p>... Please collabore...</p>
  <h2>Old results in 2012</h2>
  <p>Supposing reliable information (see sources),</p>
  <ul>
  <li><em>supported formats</em> (by tablets plus strict e-readers): PDF and EPUB. I kick around ~90% PDF, ~80% EPUB.</li>
  <li><em>downloads</em> (only e-book sales, global): PDF, EPUB and (only USA market) MOBI. I kick around ~50% PDF, ~40% EPUB.</li>
  <li><em>availability</em> (only public domain e-books): PDF and EPUB. I kick around ~90% PDF and TXT, only ~10% EPUB.</li>
  </ul>
  <p><strong>CONCLUSION</strong>:</p>
  <ul>
  <li><p>if my software problem is &quot;<em>what e-book formats to offer</em>&quot;, I need to check my public. <strong>For non-USA public, EPUB is the only format</strong>. For USA public, EPUB and MOBI. <br>NOTE: it is for &quot;<em>e-book demand</em>&quot;, but, check your public and their necessities. Nowadays, a printed book is also a necessity, people still like to use paper. PDF (with adequate paper size) may be a good option for generic (paper plus e-book) demands.</p>
  </li>
  <li><p>if my problem is &quot;<em>what e-book formats to accept</em>&quot; (ex. Receiving e-books to build a library), there are more options, and some conversion problems to solve with software.</p>
  </li>
  <li><p>if there are no software problem, is only to say &quot;the standard is&quot; or &quot;the most popular is&quot;. You can say: &quot;the most disponible is PDF&quot;, &quot;the most acceptable are PDF and EPUB&quot;, and, <strong>in strict sense, EPUB is the most popular, the <em>de facto</em> standard e-book format</strong>.</p>
  </li>
  </ul>
  <h2>Sources</h2>
  <p>(Please edit here to correct or to add more sources)</p>
  <p>Supposed to reliable/medium/informal sources by context (formal/informal), databases (general/strict), etc.</p>
  <p>1 -  <strong>Reliable sources</strong></p>
  <p>1.1. <a href="http://en.wikipedia.org/wiki/Comparison_of_e-book_formats" rel="nofollow noreferrer">Wikipedia Comparison of e-book formats</a>: show that EPUB and PDF are the most widely supported formats.</p>
  <p>1.2. <a href="http://en.wikipedia.org/wiki/E-book#Market_shares" rel="nofollow noreferrer">Indicated as reliable by Wikipedia at market share information</a>:</p>
  <p>1.2.1. Goldman Sachs 2010 report cited by <a href="http://www.bloomberg.com/news/2011-03-22/barnes-noble-is-said-to-be-likely-to-end-search-for-buyer-without-a-sale.html" rel="nofollow noreferrer">Quantity market shares of e-book sales in US</a>: with Amazon (58%) and Barnes&amp;Noble (27%) dominating. Amazon offers MOBI, the others EPUB.</p>
  <p>1.2.2. <a href="http://www.ipsos-na.com/news-polls/pressrelease.aspx?id=5399" rel="nofollow noreferrer">Market share of e-readers in Canada by Ipsos Reid at January 2012</a>: Kobo 46% (EPUB), Amazon 24%  (MOBI) and Sony 18% (EPUB) dominating.</p>
  <p>1.3. With sources <a href="http://en.wikipedia.org/wiki/Tablet_computer" rel="nofollow noreferrer">cited by Wikipedia, at <em>Tablet computer</em></a>, &quot;As of October 2012, the top-selling tablet is Apple's iPad with 100 million units sold, (...) followed by Amazon's Kindle Fire with 7 million, Barnes and Noble's Nook 5 million, and Google's Nexus 7 with 3 million units.&quot;: Apple, Nook and Nexus are EPUB, so <strong>EPUB represent more than 95% of Tablet market</strong> (and MOBI less than 5%).</p>
  <p>1.4. <a href="http://www.scielo.org/" rel="nofollow noreferrer">SciELO Library</a>: in November 2012 there were 377772 (378 thousand) articles in PDF and EPUB format.</p>
  <p>2 -  <strong>Informal sources</strong></p>
  <p>2.1. <a href="http://www.gutenberg.org" rel="nofollow noreferrer">Project Gutenberg Library</a>: over 40000 (40 thousand) books in TXT, and less into other formats, including EPUB and MOBI.</p>
  <p>2.2. <a href="http://blog.smashwords.com/2010/02/most-popular-ebook-formats-revealed.html" rel="nofollow noreferrer">Smashwords bookstore 2010 statistics</a>: counting selling/download, 35% PDF, 22% EPUB, 15% MOBI, 9% TXT.</p>
  <p>2.3. <a href="http://toc.oreilly.com/2009/01/format-comparison-pdf-epub-and-mobi-downloads-from-ebook-bundles.html" rel="nofollow noreferrer">O'Reilly bookstore 2009 statistic</a>: shows PDF and EPUB dominating.</p>
  <p>2.4. <a href="http://manybooks.net/format_stats.php" rel="nofollow noreferrer">Manybooks bookstore online statistics, counting since 2009</a>: PDF (24%), EPUB (22%) and MOBI (10%) dominate.</p>
  <hr />
  <p> (initial content adapted from <a href="https://stackoverflow.com/a/13488430/287948">SO</a>)</p>
  
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2021-02-05T11:05:09.250Z
Answers.LastActivityDate: 2021-02-05T11:05:09.250Z
Answers.UserDisplayName: Peter Krauss
Body: <p>It is a basic and old question...</p>
  
  <p>There was a "<a href="https://en.wikipedia.org/wiki/Format_war" rel="noreferrer">format war</a>" for ebooks (a "<a href="https://en.wikipedia.org/wiki/Tower_of_Babel" rel="noreferrer">Tower of eBabel</a>" for users)... EPUB won?
  <br/><a href="http://en.wikipedia.org/wiki/Comparison_of_e-book_formats" rel="noreferrer">Wikipedia says that</a> &nbsp; «<em>... EPUB format is the most widely supported vendor-independent XML-based (...) is supported by the largest number of e-Readers (...). The popularity of Amazon.com's Kindle devices in United States has led also to the prominence of KF8 and AZW</em> » ... <strong>It is a truth for this "Ebook  publishers and readers" community?</strong></p>
  
  <p>So, putting in other words:</p>
  
  <ol>
  <li><strong>EPUB is a world-wide consensus?</strong> It is the most popular, for ebook readers today? We can put all money in this format?  </li>
  <li><strong>And about the "second place", what is the format? (PDF? MOBI?)</strong> This second format is still important for ebook-readers?  <strong>There are reliable and <em>updated</em> statistics?</strong> (<a href="http://www.johndcook.com/blog/2010/07/20/e-book-formats/" rel="noreferrer">2010 example</a>, <a href="http://toc.oreilly.com/2009/01/format-comparison-pdf-epub-and-mobi-downloads-from-ebook-bundles.html" rel="noreferrer">2009 example</a>)</li>
  </ol>
  
  <hr>
  
  <h3>NOTES (EDIT)</h3>
  
  <p>The question is about <em>"Comercial + Public Domain"</em> content.</p>
  
  <p>For public libraries and public domain content the <a href="http://libraries.pewinternet.org/files/2012/06/Have-you-ever-wanted-to-borrow-a-particular-ebook_not-compatible-ereader.jpg" rel="noreferrer">perception statistics are  changing</a>... People feel that there are "some standard" (EPUB?). </p>
  
  <p>What we have heard (since 2009) in the comercial scenario is «<em>PDF is still the format of choice for most people, though EPUB is getting respectable usage, with Mobi in third</em>», but no reliable statistics about it.</p>
  
  <p>To join "public domain scenario" with "comercial scenario" perhaps another kind of statistics must be also used: a survey like <em>"ebook users read more comercial or public content?"</em></p>
  
  <p>The world-wide statistics have distinct profile than USA-statistics, but most of the compiled data came from USA.</p>
  
  <p>About replacement of the old and stiff PDF by EPUB, we have heard that "the market" is waiting the advent of <a href="http://www.w3.org/TR/html5/" rel="noreferrer">HTML5</a> + <a href="http://www.w3.org/TR/css3-page/" rel="noreferrer">CSS3-paged</a> completion (be terminated and official W3C recommendations) and consolidation... How many years?</p>
  
  <p>About reference numbers: how many ebook-titles user have (at Internet) in each format and each scenario?</p>
  
  <ul>
  <li><p>Public domain and open content:</p>
  
  <ul>
  <li><p>PDF: a lot of titles (!!) ... some reliable statistics?</p></li>
  <li><p>EPUB: as of March 2014, <a href="https://en.wikipedia.org/wiki/Project_Gutenberg" rel="noreferrer">Project Gutenberg claimed over 45,000 items</a> in its collection (but <a href="http://www.gutenberg.org/wiki/Gutenberg:Readers&#39;_FAQ#R.9._I_searched_for_a_book_I_know_is_in_Project_Gutenberg.2C_but_got_no_results." rel="noreferrer">have no format-download statiscs</a>); <a href="http://books.scielo.org/" rel="noreferrer">SciELO</a> and many other minor public domain e-book projects are also distributing ebooks. Another source of Ebooks, scientific articles: <a href="https://en.wikipedia.org/wiki/PubMed_Central" rel="noreferrer">PubMed Central</a> have 3.1 MILLION articles that now (2014) are ditributed also in EPUB format.</p></li>
  </ul></li>
  <li><p>Comercial universe: ...? Amazon dominates?</p></li>
  </ul>
  
Comments.ContentLicense: CC BY-SA 3.0
Comments.CreationDate: 2014-09-16T00:52:49.067Z
Comments.Text: "The market" never waits for "terminated and official W3C recommendations". HTML5 is a solid standard, and I don't believe CSS3-paged is even relevant.  Heck, we're using email standards that have been "proposed" for over 10 years!
Comments.UserDisplayName: Auspex
Comments.ContentLicense: CC BY-SA 3.0
Comments.CreationDate: 2017-06-06T22:02:58.537Z
Comments.Text: Possible duplicate of [Does a “one-fits-all” file format exist or should I offer multiple ebook formats?](https://ebooks.stackexchange.com/questions/92/does-a-one-fits-all-file-format-exist-or-should-i-offer-multiple-ebook-formats)
Comments.UserDisplayName: Sekhemty
Tags: <file-format>
Title: eBook format in nowadays: EPUB is de facto standard?
UserDisplayName: Peter Krauss
ThreadText: # eBook format in nowadays: EPUB is de facto standard?
  
  (Asked by: username_0 on 2014-08-19)
  
  It is a basic and old question...
  
  There was a "[format war](https://en.wikipedia.org/wiki/Format_war)" for ebooks (a "[Tower of eBabel](https://en.wikipedia.org/wiki/Tower_of_Babel)" for users)... EPUB won?
    
  [Wikipedia says that](http://en.wikipedia.org/wiki/Comparison_of_e-book_formats)   «*... EPUB format is the most widely supported vendor-independent XML-based (...) is supported by the largest number of e-Readers (...). The popularity of Amazon.com's Kindle devices in United States has led also to the prominence of KF8 and AZW* » ... **It is a truth for this "Ebook publishers and readers" community?**
  
  So, putting in other words:
  
  1. **EPUB is a world-wide consensus?** It is the most popular, for ebook readers today? We can put all money in this format?
  2. **And about the "second place", what is the format? (PDF? MOBI?)** This second format is still important for ebook-readers? **There are reliable and *updated* statistics?** ([2010 example](http://www.johndcook.com/blog/2010/07/20/e-book-formats/), [2009 example](http://toc.oreilly.com/2009/01/format-comparison-pdf-epub-and-mobi-downloads-from-ebook-bundles.html))
  
  ---
  
  ### NOTES (EDIT)
  
  The question is about *"Comercial + Public Domain"* content.
  
  For public libraries and public domain content the [perception statistics are changing](http://libraries.pewinternet.org/files/2012/06/Have-you-ever-wanted-to-borrow-a-particular-ebook_not-compatible-ereader.jpg)... People feel that there are "some standard" (EPUB?).
  
  What we have heard (since 2009) in the comercial scenario is «*PDF is still the format of choice for most people, though EPUB is getting respectable usage, with Mobi in third*», but no reliable statistics about it.
  
  To join "public domain scenario" with "comercial scenario" perhaps another kind of statistics must be also used: a survey like *"ebook users read more comercial or public content?"*
  
  The world-wide statistics have distinct profile than USA-statistics, but most of the compiled data came from USA.
  
  About replacement of the old and stiff PDF by EPUB, we have heard that "the market" is waiting the advent of [HTML5](http://www.w3.org/TR/html5/) + [CSS3-paged](http://www.w3.org/TR/css3-page/) completion (be terminated and official W3C recommendations) and consolidation... How many years?
  
  About reference numbers: how many ebook-titles user have (at Internet) in each format and each scenario?
  
  * Public domain and open content:
  
    + PDF: a lot of titles (!!) ... some reliable statistics?
    + EPUB: as of March 2014, [Project Gutenberg claimed over 45,000 items](https://en.wikipedia.org/wiki/Project_Gutenberg) in its collection (but [have no format-download statiscs](http://www.gutenberg.org/wiki/Gutenberg:Readers'_FAQ#R.9._I_searched_for_a_book_I_know_is_in_Project_Gutenberg.2C_but_got_no_results.)); [SciELO](http://books.scielo.org/) and many other minor public domain e-book projects are also distributing ebooks. Another source of Ebooks, scientific articles: [PubMed Central](https://en.wikipedia.org/wiki/PubMed_Central) have 3.1 MILLION articles that now (2014) are ditributed also in EPUB format.
  * Comercial universe: ...? Amazon dominates?
  
  **Tags:** file-format
  
  > **Comments:**
  > **username_1**: "The market" never waits for "terminated and official W3C recommendations". HTML5 is a solid standard, and I don't believe CSS3-paged is even relevant.  Heck, we're using email standards that have been "proposed" for over 10 years!  
  > **username_2**: Possible duplicate of [Does a “one-fits-all” file format exist or should I offer multiple ebook formats?](https://ebooks.stackexchange.com/questions/92/does-a-one-fits-all-file-format-exist-or-should-i-offer-multiple-ebook-formats)  
  
  ---
  
  ## 3 answers
  
  ### Answer by username_3 on 2014-08-24. Score: 7
  
  First, a note: I will not be considering PDFs in this answer, because I do not consider PDFs to be ebooks. There are a number of reasons for this, like lack of reflowability and end-user customization options, but the primary reason is that PDFs are not generally sold at sites that sell ebooks--you can't sell your PDFs through iBooks or the Kindle store or whatnot. Others have other opinions, and that's fine—the relevant info is that I won't be considering PDFs here.
  
  In terms of variety of devices supporting the format, epub is the clear standard—it's supported on nearly everything that reads ebooks. When you look at numbers, though, it's a different story: according to [an article](http://www.digitalbookworld.com/2013/bisg-report-a-few-more-ebook-stats/) at Digital Book World, a recent Book Industry Study Group found the following statistics to the question "Where do you typically acquire ebooks?":
  
  ```
  Amazon.com website: 51.3%
  Amazon App: 15.7%
  iBooks/iTunes (Apple): 8.2%
  Barnes & Noble App: 6.1%
  Barnes & Noble website: 5.7%
  All other sources: 12.8%
  
  ```
  
  This means that Amazon accounts for roughly 2/3 of the sales of ebooks, making their proprietary mobi/KF8 format the dominant format.
  
  In essence, there is no "winner" yet, and there is not likely to be any time soon. Apple, Google, Barnes & Noble, and Kobo are enough to ensure that epub will remain alive and kicking for quite some time. With a majority of the sales, Amazon has no impetus to switch to a standard, and they don't appear to be in any danger of losing much market share. Where we are is where we're likely to be for quite a while, which means making two formats: epub and mobi/KF8. fortunately, Amazon has gotten much better at making tools that convert from epub to their format, so concentrating on epub will give you something for Amazon as well with little extra work.
  
  > **Comments:**
  > **username_0**: Thanks, this is a good starting point (!)... But it is incomplete without public domain content, and without non-USA e-commerce statistics. Example: [As of March 2014, Project Gutenberg claimed over 45,000 items in its collection](https://en.wikipedia.org/wiki/Project_Gutenberg) (but [not have any format-download statiscs](http://www.gutenberg.org/wiki/Gutenberg:Readers'_FAQ#R.9._I_searched_for_a_book_I_know_is_in_Project_Gutenberg.2C_but_got_no_results.)); [SciELO](http://books.scielo.org/) and many other minor public domain e-book projects are also distributing ebooks.  
  > **username_0**: Another non-usual but growing source of e-books are  scientific articles: [PubMed Central](https://en.wikipedia.org/wiki/PubMed_Central) have 3.1 MILLION Articles that now (2014) are ditributed also in EPUB format.  
  > **username_4**: How about software support? As I read around, epub seems to be a much more popular format to create books (even if Kindle coverts it to mobi).  
  > **username_3**: Epub is a much more popular way to create ebooks because Amazon's format is proprietary; you can't directly make it. You can only convert to it from epub or a few other formats.  
  > **username_4**: @username_3 That would be sad if the dominant format would be something that needs another even just for creation. Even PDF is more open in that sense.  
  > **username_3**: @username_4: 1000% agreed; that's why I don't ever buy books from Amazon. They're proprietary and terrible.  
  > **username_5**: @username_3 they are easily converted from Kindle format to epub by programs like calibre  
  > **username_3**: Sure, but given the option, why support a company that does stuff I don't approve of?  
  > **username_1**: Public domain content is not really relevant. Almost all such content will be initially EPUB, but EPUB to MOBI and MOBI to EPUB are so trivial, that until Amazon finally kills off all competition, everything available in MOBI/AZW/KF8 will be available in EPUB and vice versa (in fact, I downloaded the same book from Amazon as AZW3 and Kobo as EPUB this week).  
  > **username_0**: Hi, perhaps some news: [do you know this estimates](https://fortunedotcom.files.wordpress.com/2015/09/2015-aug-trend-units.png)? They are come from [this article](http://fortune.com/2015/09/24/ebook-sales/).  
  > **username_0**: Hi, come 2020 news about the theme, new statistics?    PS: for my last comment, correcting [2015 chart estimatives link](https://content.fortune.com/wp-content/uploads/2015/09/aap-unit-sales.png).  
  
  ---
  
  ### Answer by username_6 on 2014-09-10. Score: 1
  
  Amazon has over 2.8 million ebooks, including nearly all public domain books. See the left hand column, which provides an update to date count of ebooks available: <http://www.amazon.com/s/ref=lp_154606011_ex_n_1?rh=n%3A133140011&bbn=133140011&ie=UTF8&qid=1410374478>
  
  This 2.8 million books makes things like Project Gutenberg statistically insignificant.
  
  Your quote that "EPUB format is the most widely supported vendor-independent XML-based" is obviously designed to exclude MOBI/Kindle from the mix, because it's not vendor-independent. And sure, outside of Amazon, it is the dominant standard.
  
  But more importantly, why do you want to know?
  
  If the answer is because you want to know what format to publish a book in, versus you want to build an eReader app, versus you're writing a research paper, there are very different implications.
  
  If you're an author publishing commercial fiction, since [Amazon has about 65% of the ebook market](http://www.forbes.com/sites/jeffbercovici/2014/02/10/amazon-vs-book-publishers-by-the-numbers/), you must publish in MOBI to be successful. If you are an indie author, Amazon has an even bigger percentage of the market for indie authors (anecdotally 80+%), and so it becomes even more crucial.
  
  If you are providing an ebook where access is crucial, e.g. a school text book that must be available to all students, then you must publish in both EPUB and MOBI.
  
  Since EPUB and MOBI can be easily converted back and forth, one might argue that the question is irrelevant. Simply provide books in both formats.
  
  > **Comments:**
  > **username_0**: Hum... a first point... I not  know how write right English  (I need help of web-translators), but *"my book" can add "+1" at Kindle Store counter*... By other hand, "my book" will never appear on Project Gutenberg. When we count "any thing" at Amazon we need to compare it with "any thing" at the *full-Internet*, not only with Gutenberg...  
  > **username_0**: You cited discussions, not reliable sources of statistics... Forbes, that cite Newyorker.com, are good sources, but there are no newer result for @username_3's answer (your 65% is the "51.3%+15.7%" of Tom's). The BISG (Book Industry Study Group cited by Tom) report is good, so what is wrong or what is what's missing? BISG is an U.S. trade association, as Amazon; and Amazon, with others, *with focus on non-public contents*, was pay BISG to produce the report... Some good results found there, and perhaps other independent report confirm the same results... So, where the "other independent reports"?  
  > **username_6**: Again, I will refer back to: What decision are you trying to make? What is the purpose of the question? Are you testifying in front of a judge? That requires a different level of reliability than say, trying to decide how and where to publish your novel.  
  > **username_0**: We develop software and offer services for "content management/styling/transform"... Some software need a 2-year plan... What will the scenery in 2 years? How will the market and the "reading habits"? Our main customers are  public domain content producers, for non-US readers... This is our reality, and is the same for many middle/small company around non-US-world.  
  > **username_1**: If that's your need, then it's a complete non-issue. Decide on a base platform (and personally, I think EPUB is the one to use) and then convert to the other for distribution to nearly 100% of the market.  
  > **username_0**: Hi, perhaps some news: [do you know this estimates](https://fortunedotcom.files.wordpress.com/2015/09/2015-aug-trend-units.png)? They are come from [this article](http://fortune.com/2015/09/24/ebook-sales/).  
  
  ---
  
  ### Answer by username_0 on 2021-02-05. Score: 0
  
  **This is a Wiki, please edit and collabore!** We need good English and updated content.
  
  ## Concepts
  
  As used here:
  
  * *e-book* and *e-book reader*: [e-book](http://en.wikipedia.org/wiki/E-book) is the content, a file; and the *e-reader* is the device, a hardware (or software+hardware). Sometimes the content (e.g. CSS or Javascript code) have some algorithmic prescriptions for e-reader.
  
    + *e-reader*: considering here that an e-reader is a "[paper substitute](http://www.ecolibris.net/ebooks.asp)" device, so a Desktop PC computer or an iPhone are not dedicated e-readers, but Kindle and a [Tablet computer](http://en.wikipedia.org/wiki/Tablet_computer) are.
  * "*usable e-book format*": in a broader sense, paper-oriented formats, like *[PostScript](http://en.wikipedia.org/wiki/PostScript)* or *[PDF](http://en.wikipedia.org/wiki/Portable_Document_Format)*, are acceptable for e-books, and can be called *e-book formats*.
  * real, strict sense **e-book format**: neither a "web format", like HTML, nor a "paper format", like PDF. The e-Books are "[paged media](http://www.w3.org/TR/css3-page/)", as paper books, but with diagramming flexibility: an e-book need to be [reflowable](http://en.wikipedia.org/wiki/Reflowable_document), a resizable content that adapts to different resolutions and different [aspect-radio screens](http://en.wikipedia.org/wiki/Aspect_ratio_(image)).   
    PS: generic HTML is not an ebook format because is not "all in only one file", but sometimes (e.g. using inline SVG and base64-encoded PNG images) HTML can be adapted for it.
  * "interactive e-book format": another growing demand for e-books are interactivity ([EPUB example](http://www.youtube.com/watch?v=nuHuotsUxyE) ), but we can ignore this demand here, in favor of the strict sense, and the necessity of [classic books](http://www.gutenberg.org/) into digital devices.
  
  So, conceptually, PDF is considered an (usable) *e-book format* because it is a legacy from old paper-oriented systems, where authors and layout designers were oriented to the paper size. As of 2012 the screen of the "e-book reader" is the final recipient of the content, and layout authoring is oriented to (some) screen adaptability.
  
  There are three important criteria — metrics to check if a format is *de facto* standard — for electing e-book format popularity:
  
  * most widely **supported formats**: between popular e-book readers, statistics about direct support (without content loss or conversion demand) for each format.
  * more **downloads**: sales and download counting, in reliable "sales statistics" at bookstores and download statistics at libraries.
  * **availability**: number of distinct online links (at online libraries and others), each link to a distinct file download of a public domain e-book. Example: number of titles into the [Project](http://www.gutenberg.org/), [SciELO](http://www.scielo.org/), etc.
  
  ## New results in 2020?
  
  ... Please collabore...
  
  ## Old results in 2012
  
  Supposing reliable information (see sources),
  
  * *supported formats* (by tablets plus strict e-readers): PDF and EPUB. I kick around ~90% PDF, ~80% EPUB.
  * *downloads* (only e-book sales, global): PDF, EPUB and (only USA market) MOBI. I kick around ~50% PDF, ~40% EPUB.
  * *availability* (only public domain e-books): PDF and EPUB. I kick around ~90% PDF and TXT, only ~10% EPUB.
  
  **CONCLUSION**:
  
  * if my software problem is "*what e-book formats to offer*", I need to check my public. **For non-USA public, EPUB is the only format**. For USA public, EPUB and MOBI.   
    NOTE: it is for "*e-book demand*", but, check your public and their necessities. Nowadays, a printed book is also a necessity, people still like to use paper. PDF (with adequate paper size) may be a good option for generic (paper plus e-book) demands.
  * if my problem is "*what e-book formats to accept*" (ex. Receiving e-books to build a library), there are more options, and some conversion problems to solve with software.
  * if there are no software problem, is only to say "the standard is" or "the most popular is". You can say: "the most disponible is PDF", "the most acceptable are PDF and EPUB", and, **in strict sense, EPUB is the most popular, the *de facto* standard e-book format**.
  
  ## Sources
  
  (Please edit here to correct or to add more sources)
  
  Supposed to reliable/medium/informal sources by context (formal/informal), databases (general/strict), etc.
  
  1 - **Reliable sources**
  
  1.1. [Wikipedia Comparison of e-book formats](http://en.wikipedia.org/wiki/Comparison_of_e-book_formats): show that EPUB and PDF are the most widely supported formats.
  
  1.2. [Indicated as reliable by Wikipedia at market share information](http://en.wikipedia.org/wiki/E-book#Market_shares):
  
  1.2.1. Goldman Sachs 2010 report cited by [Quantity market shares of e-book sales in US](http://www.bloomberg.com/news/2011-03-22/barnes-noble-is-said-to-be-likely-to-end-search-for-buyer-without-a-sale.html): with Amazon (58%) and Barnes&Noble (27%) dominating. Amazon offers MOBI, the others EPUB.
  
  1.2.2. [Market share of e-readers in Canada by Ipsos Reid at January 2012](http://www.ipsos-na.com/news-polls/pressrelease.aspx?id=5399): Kobo 46% (EPUB), Amazon 24% (MOBI) and Sony 18% (EPUB) dominating.
  
  1.3. With sources [cited by Wikipedia, at *Tablet computer*](http://en.wikipedia.org/wiki/Tablet_computer), "As of October 2012, the top-selling tablet is Apple's iPad with 100 million units sold, (...) followed by Amazon's Kindle Fire with 7 million, Barnes and Noble's Nook 5 million, and Google's Nexus 7 with 3 million units.": Apple, Nook and Nexus are EPUB, so **EPUB represent more than 95% of Tablet market** (and MOBI less than 5%).
  
  1.4. [SciELO Library](http://www.scielo.org/): in November 2012 there were 377772 (378 thousand) articles in PDF and EPUB format.
  
  2 - **Informal sources**
  
  2.1. [Project Gutenberg Library](http://www.gutenberg.org): over 40000 (40 thousand) books in TXT, and less into other formats, including EPUB and MOBI.
  
  2.2. [Smashwords bookstore 2010 statistics](http://blog.smashwords.com/2010/02/most-popular-ebook-formats-revealed.html): counting selling/download, 35% PDF, 22% EPUB, 15% MOBI, 9% TXT.
  
  2.3. [O'Reilly bookstore 2009 statistic](http://toc.oreilly.com/2009/01/format-comparison-pdf-epub-and-mobi-downloads-from-ebook-bundles.html): shows PDF and EPUB dominating.
  
  2.4. [Manybooks bookstore online statistics, counting since 2009](http://manybooks.net/format_stats.php): PDF (24%), EPUB (22%) and MOBI (10%) dominate.
  
  ---
  
   (initial content adapted from [SO](https://stackoverflow.com/a/13488430/287948))
  
  
  ---
  
  