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This prior question is about the differences between EPUB 2 and EPUB 3.

What is more interesting to me, as an owner of three different EPUB 2 devices, is: can EPUB 3 files, and particularly the book text parts, be rendered on a EPUB 2 reading systems (of course dispensing with EPUB 3 specific features)?

Can all such files be rendered, or do they need special setup? Assuming compatibility is possible, is there software already supporting generation of such EPUB 3 files compatible with EPUB 2 reading systems?

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    While it is not practical in many cases, the epub documents can be manually edited to remove any epub3 specific functionality. I've been forced to do something similar where I had to remove javascript code that only worked on a Kobo Reader. On my Sony Reader, the epub would not render properly (very large text where a single word would take up the entire screen). – Jason Down Dec 20 '13 at 22:39
  • @JasonDown I know about changing EPUBs manually, but did not think about doing that for this purpose. I was more looking at buying an EPUB 3 book file and it being usable at is. But thanks for the suggestion! – Anthon Dec 21 '13 at 5:31
  • You are asking two questions here. The last sentence should be a separate question – user151019 Dec 22 '13 at 13:43
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    @Anthon. No problem. I learned quite a lot about epub files by opening them up and playing around with them. – Jason Down Dec 23 '13 at 13:46
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The IDPF states the following in a thread about EPUB 3 Rendering in EPUB 2 reading systems

Although EPUB 3 is not perfectly backwards compatible with EPUB 2, a goal of the recent revision was to ensure, as much as possible, a basic level of rendering when features overlap.

The thread particularly mentions that providing the NCX data is necessary, which has been superseded with EPUB Navigation Documents as described in the EPUB 3 changes document

So, if some care is taken, EPUB 3 files can be made to render on EPUB 2 reading systems.

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Your best bet is to ask before you buy.

It depends on the reason the book was released in the EPUB 3 format. If it's a static text, and the publisher was only trying to follow the latest guidelines and standards, they may have added the extra bits required by the older standard, so it would degrade gracefully and be available to more customers.

If, on the other hand, the book was released as an EPUB 3 in order to take full advantage of the standard's dynamics and interactivity, it's likely that the publisher didn't add the required legacy information. They might have pegged a particular device, to ensure that the book would function predictably. For example, Walrus Books released H.P. Lovecraft's novel, "Kadath", for the iBooks app in EPUB 3. It is highly interactive and intended for the iPad. They had no reason to make it work on other devices, and probably didn't bother with legacy shims.

Regarding your question about software, I'm not aware of a good GUI for creating EPUB 3s. I use Dreamweaver to modify the HTML, CSS, and JavaScript code directly, and ePubPack and 7zip to pack and unpack it. Then I test it with ePubCheck.

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I just wanted to add that Nook is able to display epub3 files (without supporting a lot of its features) and Kindle Previewer (the tool that converts epub to kindle format) will accept epub3 files for conversion. Again, the latest Kindle devices don't support a lot of optional epub3 features, but it can still display it. Same for ibooks.

Smashwords is iffier (although I haven't checked recently). A year ago I noticed that they were using an outdated version of epubcheck which flagged as errors any epub3 file. I noticed this first in 2012, noticed that it still had not been fixed by Smashwords as of Oct 2013, so it may have been fixed by now. [2017 Update: Smashwords has fixed this].

  • You have provided the same answer for two separate questions (ebooks.stackexchange.com/questions/974/…). This is generally frowned upon. From what I can tell the first part of your answer fits this question and the second part fits the other answer. Please consider revising your answers or removing one of the answers (you could leave a comment that links to the other answer). – Jason Down Feb 24 '14 at 19:02

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