Skip to main content

Duolir Lets You Read a Dual-Language eBook With Instant Translations

duolirMany readers challenge themselves with books in other languages. Usually they have to install a translation dictionary in order to catch the nuances, but there are other options.

Yesterday a friend on Twitter pointed me at Duolir, an iOS app which offers an instantaneous translation feature.

While instant translation is nothing new, most current examples involve mechanical translation of the text;  an article is fed through either Google or Bing Translate and the result is spat out – errors and all.

Duolir goes one step better.  This platform offers dual-language ebooks which have been specially made so you can click on each sentence and read the sentence in another language.

In practice it looks something like this:

That’s a nifty trick, but it’s not exactly a new one.

Google does something similar with Google Translate, and you can also find ebooks like the ones in Duolir on another site, DoppleText. Those ebooks work in (almost?) any app which supports Epub. They also reportedly work on the Kindle, but I would test that first.

I was also told on Twitter that a French publisher had shown a proof of concept several years ago. That example reportedly used Javascript in Epub3, although I haven’t found a file which shows it. (Thanks, Jiminy!)

If you would like to see a similar trick in action, posted a demo ebook. It doesn’t work quite the same as Duolir, but it does work in iBooks and in the Menestrello app. (Thanks, Alberto!)

The translations look like this:


This is a pretty well-known trick, so you’re probably wondering why it’s not more widely used.

While Duolir offers around 50 titles, and Doppletext has around 40 public domain titles, that’s just a drop in the bucket in comparison to the hundreds if not thousands of books where this could be used.

If I had to guess, I’d bet that the cost of making the ebook is probably the killer. There isn’t a huge market for this feature, not compared to releasing two separate single language ebooks, so it is difficult to justify the expense.

And that’s a shame, because on a technical level this is nifty.

Similar Articles


DuoLir ou la lecture en deux langues | Quoi lire ? March 23, 2015 um 4:01 pm

[…] Voici une application pour iOS que j’ai découvert par The Digital Reader. […]

deanishe March 23, 2015 um 4:31 pm

i imagine there’ll be quite some demand for the books (at least with English as one of the languages).

Other folks are an awful lot keener on learning our language than we theirs. And English is a valuable skill that can add a chunk to your salary.

Demand won’t be as high for two separate books, as you say, but these book are potentially much more valuable.

Existing paper equivalents sell for 7-8x what the monolingual version does (for public domain titles, not the latest releases).

Michael March 23, 2015 um 10:54 pm

Very cool. I think ebook setups like these could find their niche somewhere like Japan, where for a long time quite a few English books have been published with accompanying glossaries and/or full study guides. I’d love to have the same in reverse for my Japanese ebooks.

Alberto Pettarin March 24, 2015 um 12:43 pm

(Discl: I’m the Head of R&D at ReadBeyond)

A small correction: the screenshot of our sample you posted shows a regular footnote, as you mentioned, not a translation. The "translation" screenshot is this one:
where tapping on [IT] or [EN] will show the translation of the corresponding passage.

The "sample" we made (available online here: ) is an attempt to support parallel texts (i.e., text + translation(s)) in a declarative way within the EPUB specification.

For this to work, the reading system must be able to "read" the mapping information (embedded into the EPUB) and leverage it — we included that in our EPUB reader app Menestrello. Tap on [IT] or [EN], and the translation will show up in the bottom panel. On any other reading system, the [IT] and [EN] links will fallback to the normal link behavior.

Our sample is quite old, and uses a naming convention to convey the mapping between the two languages, but now IDPF has published the EPUB 3 Multiple Renditions specification, which is able to achieve the same goal. (When Reading Systems will implement it, of course.)

Other approaches include JS code (as DoppleText does) or encapsulating the translation information in a proprietary format, rendered by a proprietary reading system (as Duolir does) — but in my view they have serious drawbacks, as they essentially "hack" the specs or just create a proprietary system where it is unnecessary.

Finally, please note that specifying the mapping in a declarative way allows the reading system/user to choose the actual type of rendition (e.g., split view vs. occasional translation in a bottom panel) or support more than two languages.


Several Italian publishers feel the problem of lack of support for parallel texts in digital format, because we have a niche of Ancient Greek/Latin/foreign texts + Italian translation, which essentially are made available only on paper because the current digital solutions do not offer a decent UX for parallel texts. To recap, I would say that the main problem for them is not the "parallelization/production" cost , but the actual support of reading systems.

Nate Hoffelder March 24, 2015 um 1:02 pm

I fixed it, thanks.

Alberto Pettarin March 25, 2015 um 5:19 am

Thank you!

Warum zweisprachige eBooks bisher erfolglos blieben (und wie sich das jetzt ändern könnte) » March 24, 2015 um 3:57 pm

[…] neue iOS-App Duolir eines holländischen Unternehmers, die The Digital Reader kürzlich vorstellte, will da Abhilfe schaffen. Entwickler Giwan Persaud erklärt auf […]

Write a Comment