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What's the point of these two ebook formats? The quality and file size of the ebooks tend to be near identical and ereaders for these aren't exotic at all.

Why would you choose one over the other?

Irregular User
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    The size of a DJVu file is on average 20 times smaller than the corresponding PDF file, if yours aren't you are using the wrong way to convert to DjVu. – Anthon Mar 05 '16 at 06:21
  • Who said that I was converting anything? – Irregular User Mar 05 '16 at 10:13
  • I was assuming that because if you don't start with the same (scanned) image based file and convert the same source to both PDF and DjVu, you are comparing apples and pears. – Anthon Mar 05 '16 at 10:44
  • @Anthon Isn't this a moot point if the quality of the ebooks are the same? If we've achieved the same quality with similar file sizes, then what's the point of one over the other is what the question is (which has now been answered). – Irregular User Mar 05 '16 at 12:52
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    No it is not. You can compare the quality of an MP3 file of piece of music with its score and they say "the music on the score is better at a smaller size". The accepted answer is just guesswork and claims that PDF is safer, are neither substantiated as well as unlikely. Please give a link to two where I can eBooks one in PDF one in DjVu with similar sizes and I'll give the analysis. – Anthon Mar 05 '16 at 15:08
  • @Anthon This is getting a bit silly now, especially with that "analogy" to my question. The accepted answer has been accepted since it's makes some satisfactory points. For a link, you're free to search the internet for such things but I won't be providing links to ebooks with questionable legality. But as it stands, I'm satisfied with the answer given and need no more on this topic. – Irregular User Mar 05 '16 at 18:17
  • @Anthon I'm not sure if a high rep user downvoting a question and answer out of anger or annoyance without suggesting edits is particularly professional, but there we go. – Irregular User Mar 05 '16 at 21:41
  • Hover over the down arrow, two of the three reasons for downvoting apply. Downvoting has nothing to do with anger, just with indicating to others what one thinks of the quality of your post. Thanks for the suggestion to do so. – Anthon Mar 05 '16 at 22:26
  • @Anthon I know how downvoting works thanks, but a downvote -after- discussion in the comment section indicates so. But a display of your mental state in a public forum is just as fine with me. – Irregular User Mar 05 '16 at 22:37
  • Philosophical question. Windows vs Linux? MS Word vs LibreOffice? The enlightened part of the population will use Djvu. Others will use the PDF because the existence of DjVu is below their distinctive ability. How the question should be? Why is the PDF expanded? - Because Adobe. And Adobe is a big corporation. – Stilgar Dragonclaw Jun 20 '18 at 23:35

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Well in my opinion and also testing knowledge of ereaders... the djvu and pdf doesn't hold that great difference anymore... In the past djvu use to have a higher compression ratio cause the files to be much smaller in storage and also had higher quality rates at this compression... Now with tech as far as now pdf is also able to have high compression ratio... Though when it comes to ereaders you see pdf is sometimes much more secured when doing DRM as such it would be more used above djvu... also I know from tft eReaders they tend to not always be able to support the djvu format that greatly where as all tft eReaders do support pdf, due to the fact that most development with eReaders ensure adobe support so that people can get DRM ebooks. E-ink readers are able to support djvu again very good so yeah on the end nowadays I would say use the format of the ebooks easiest for you to obtain :D

I hope that my explanation help a bit. This is my personal opinion from my experience of testing across different eReader devices and E-ink as the company I work for use to back in the day import them when they were big in the market and I was lead tester for many of these devices :)

Also seeing now the title you wanted advantage and disadvantages... okay well then

pdf: safer, more secured, available across more platforms, but more detail slower loading, refresh ratio is low

djvu: better caching for E-ink, redraw faster, graphical book, not as secured, not available on many different platforms

Heartless68
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    What new technology in PDF are you referring to? – Anthon Mar 05 '16 at 10:43
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    There is multiple new development in what gets add on functions with pdf in 1993 it was just a plain format in 1996 it introduced the whole interaction feature later on custom signature, then also more security etc not going list everything now but if you want to read more about it check out: www.prepressure.com/pdf/basics/history sorry for the late response – Heartless68 Mar 06 '16 at 20:51
  • PDF spec contains JavaScript, supports dynamic content known to have security holes, and specifies many features too vaguely for developers to reliably implement in a way that is reliably unexploitable. Even in Adobe's own Acrobat Reader, new exploits are discovered constantly. About the only thing less safe than opening a PDF file is running an unknown executable. – skylize Mar 16 '23 at 19:34