oreillychart Andrew Savikas of O’Reilly has posted a very interesting chart of the breakdown of format downloads by percentage of O’Reilly books for the last two years. The chart shows PDFs falling from around 90% of the total to around 50%. The sharpest drop in PDF happened around the end of 2008, and the decline has been more or less stady since then (save for a big spike brought on by an “any book for $9.99” promotion earlier this year).

The biggest gain has been seen by EPUB format, which seems to account for about 25%, followed by Mobipocket with a respectable 15% or so (not too surprising given that this is the format of the Kindle). Android application files and DAISY files make up the remainder.

Much like Baen’s, O’Reilly’s e-book sales include the right to download DRM-free versions of the book in any available format—someone who has bought an O’Reilly book might download just one format or several depending on their needs.

The chart tracks the total number of downloads in all formats, but does not reveal increases or decreases in overall unit sales (though Savikas notes “we’re already running well ahead of last year’s full-year total with a quarter still to go”). As some commenters point out, this makes it hard to figure out whether the total quantity of PDFs being downloaded has gone down, or whether it’s just that more people are downloading other formats too.

Still, I think that the rise of alternative formats is probably attributable to the rise of e-book reader apps and devices that use those formats—the Kindle’s Mobipocket and most other readers’ EPUB have shown the biggest increases, while mostly-read-on-computer-screen PDFs have been going down. It will be interesting to see what the trend looks like in another two years.

(Found via EBookNewser.)


  1. I wonder if downloads of PDF would increase if it was possible to “resize” them to fit on the screens of some ereaders like the Kobo. Also if authors had access to a free/cheap PDF editor to take existing books and redo them in a 6″ screen size.

  2. Carol A has identified why PDF is one of the worst formats ever for electronic files. It is a pain in the @ss to rewrap, scale, or even read on the vast majority of electronic devices. PDF was designed basically for business documents that look like 8.5 x 10 inch paper. Looks great when printed out in your office. I have read countless scientific and technical PDFs for work over the years, and if I could simply get rid of them all for a nice ePub, I would be happy.

    I get the feeling that many authors like PDFs because they can make their books look like they would like them to look if they were printed. For those of us who don’t like to read on paper anymore, we want documents to be easily manipulated to show the information on any sized display. This eliminates PDF as a workable format. ePub in many ways allows the authors to make their creative works look beautiful and still look good on lots of devices.

  3. Carol I would suggest that resizing is the worst thing we need because it just makes the type microscopic. It would need to completely reflow the text, which is completely against the structure of a pdf which was designed for big screens.

    The issue of formats is, imho, a critical one. When the sales of eBooks are aimed at the masses of mainstream readers in 2011 and 2012, the mainstream public will most certainly NOT appreciate the confusion. The public likes one or at the most two choices of format or it holds back and stays away. The history of music and video formats is a salutary lesson.

    I really believe it would help the mainstream adoption of eBooks enormously if the industry could sit down and agree on a single format. One that could be flexible and then upgraded in time if needed.

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