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I am having a large chm file, over 40 MB available here. I want to read this file in my Android mobile, there are some chm reader apps available which I am using for this purpose.

But none of them are working on this one, because its size is too big. Is there a way, I can split this chm file into smaller size?

I would prefer if there is some software available for doing this, but if it can be done programatically, I would try that too...

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Have you tried FBReader? – Karan Jun 10 '13 at 22:03
up vote 0 down vote accepted

HTML Help is a proprietary format that's been reverse-engineered by people. If none of your Android apps can open a big CHM, one option might be to use CHM Decoder to decompile the file into its constituent HTMLs (be sure to select the Generate Menu checkbox):


Once you copy all the extracted files over you should be able to open the top-level HTML index file in any Android browser.

If you must have multiple compiled CHMs that contain portions of the original file, you can use the HTML Help Workshop to decompile, separate and recompile as required.

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I want to be able to get back the decoded/splitted file back into CHM format. So, I won't prefer reading HTML files, as Java already provides html API... – Prateek Singla Jun 11 '13 at 7:48
As I stated above, that can be done but you'll need to learn how to use HTML Help Workshop for it. – Karan Jun 11 '13 at 14:37

Take a look at calibre, it's great for converting all sorts of digital text media. I'm pretty sure you can use it to split your file into smaller pieces.

If that doesn't go far enough for you, sigil is a true epub editor.

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No, it doesn't work to split the chm files into smaller ones, it can only convert it to other formats. – Prateek Singla Jun 10 '13 at 11:24
If calibre doesn't suffice, sigil ( should be your next stop. It's a true epub editor. Added it to my original answer. – SBI Jun 10 '13 at 11:27
I want to retain the bookmark structure in chm and then, I should be able to split it into smaller size, converting it into epub and then splitting and then converting back to chm may cause loss of bookmark structure... However, I will give it a try... – Prateek Singla Jun 10 '13 at 11:31
chm being proprietary, I'm not even sure how editable that file is by itself. However, ToC should remain intact when you convert. – SBI Jun 10 '13 at 11:34

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