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Home / HTMLZ Support for single packaged zip file


Hi Guys - Greetings and Best Wishes for 2020,

Is there any chance of support for the htmlz package. Normally I have to unzip them first to read them - would be nice to just read them from the single file. Seems like basic html so not much different to the epub package ???. Tried renaming it to epub but it didn’t work

Love Sumatra - thanks everyone


I will leave the official response to the one active developer @kjk

However in order to support that format there are a few issues

  1. optionally those files include metadata such as OPF format
    The first feature request will be reading and editing such variable data

  2. the format of HTML changes so the current incarnation is HTML5 which includes supporting media etc etc, IF only raw functionality is included there will be hundreds of this file does not work etc.

  3. Most complaints about the epub reader engine and recent files that use the .css for apperance modifications is that “they dont look the same in SumatraPDF”. That can (and may be ?) improved however it takes a lot of coding time away from other important bug fixes etc.

In summary the files could be easily “READ” but the first complaint is it wont look “RIGHT”


Could you provide more information:

  1. What software creates those .htmlz files? How popular they are?

  2. Where can I get samples of such files for testing?


see where it states as considered “obsolete” most commonly produced by various online converters and calibre

I think it might be “a lot of pain for little gain” unless a major publisher like Amozon takes it up.


Ok, Thanks for the response. I am only recently coming across these files. Seems the format was developed by one of the Calibre developers. (see link) I don’t know how popular it is. There seems a bit of support for it judging by the online conversion web pages. It seems that it was developed as an amendment to the epub package to allow the html in a single file instead of split files - thus allowing easier editing of the book for those who needed to do so.

Some sample files here.

Thanks & Cheers


@kjk looking at the simple structure these were a basic epub format and although MuPDF does not handle the htmlz file extension the internals appear to be understood and well handled as if they are a variant of FictionBook

So unpack the zip in temporary memory and render the book.htm as if it were book.fb2. MuPDF does show bookmark locations but seems to get them wrong possibly due to reflowable locations?