How to confirm if ePub is DRM'ed ? Kobo Aura HD possibly refusing to read DRM-free ePub

Question

I've got an ePub file that I'm quite certain has no DRM on it. It's a DRM-free book bought from O'Reilly. However, my Kobo Aura HD is refusing to use it, saying that it's Adobe DRM'ed and I have to log in.

So, first thing I tried to confirm is that it is DRM-free. Unzipping the ePub, it has no rights.xml file, no encryption.xml file, and all the content is available through plain html files. epubcheck does't say anything about it having DRM. Is this sufficient to confirm that an ePub is DRM-free?

Second, if it is indeed DRM-free as it should, then the Kobo Aura HD is incorrectly indicating that it has DRM. It is refusing the display the file even though it displays fine in every other reader I've tried, including iBooks and Calibre, neither of which I've logged into any accounts.

Any remedies that I can use to fix this? Perhaps somehow repackage the ePub?

Answer 1

I have a different type of Kobo (Glo HD), and no knowledge of DRM implementation for ePub, though I would expect that a variety of distinct DRM techniques can be used on ePub files.

I would however expect that an eBook from O'Reilly does not carry DRM. So your problem should have another cause. Which you apparently confirmed by testing on different devices or application software.

What I noticed by experimenting with my Kobo is that, when an eBook has been loaded and made visible to the Kobo, it may interpret reading problems as caused by the presence of DRM, though that may not be the case. And you get an error message that pretends that the book is DRM protected.

Typically that can happen if some mishap destroys the file or moves it to another directory in the Kobo memory. That is easily done by accessing the memory directly, as done by tools such as Calibre, though this should in no way be construed as suggesting that Calibre makes such mistakes.

From what I understood experimentally (so I may be wrong) The Kobo believes it has a DRM problem with that eBook until it does a scan of its memory, and refreshes its tables, which will then no longer point to a missing ePub file. I am not sure what is the best way to force that scan. The way I did it was by using the Kobo browser to download in the Kobo a DRM-free book (I usually go to http://gutenberg.org for that).

So it could be that your Kobo has some problem reading the file, for whatever reason, and interprets it as a DRM problem, exactly as it did for my missing/displaced files.

My idea is not to give you a definite answer on what is wrong, as only you can do that. It is more to suggest that the Kobo may interpret as a DRM problem a problem unrelated to DRM.

Answer 2

I had the same problem with my kobo glo HD with that epub https://docs.spring.io/spring-boot/docs/2.0.0.M5/reference/epub/spring-boot-reference.epub It's drm free.

but not with that one and many other epubs :

https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/7/epub/7.4_release_notes/Red_Hat_Enterprise_Linux-7-7.4_Release_Notes-en-US.epub

I have tried to download from kobo web browser, upload from my computer many times and it was not working so I did a check on

http://validator.idpf.org/

and it tells me content.opf were missing. I checked it by my self and the path was incomplete in the META-INF/container.xml file. So I wrote the full path to content.opf did a new check then upload the file on my kobo again and it works.