zim-tools VS libzim

It looks like Kiwix uses the ZIM file format, which appears to have diffing support [0] (see zimdiff and zimpatch). That said, it doesn't look like Kiwix actually publishes those diffs.

[0] https://github.com/openzim/zim-tools/tree/master/src

One problem that remains is to bring the access to insight webpage to the ".zim" format that the kiwix app can process. Here it seems the only way to do that is a tool called "zimwriterfs" that can be found in another opensource project that defines the basis of the offline reader format and is used by kiwix I believe. https://github.com/openzim/zim-tools ...this was no problem for me, as the tool can be accessed easily from standard linux distributions like ubuntu. Creating the .zim file from the unzipped access to insight offline version is a single command line, after preparing a little icon that will be used for the site in kiwix. There seems to be no windows version of that tool available though...

More info at https://github.com/openzim/zim-tools

I meant the Kiwix dump (https://download.kiwix.org/zim/wikipedia_en_all_nopic.zim – careful, 60GB!).

At a first glance, the Wikimedia XML dump does not look substantially different from what Kiwix/ZIM does with compressed HTML: They're both compressed (bz2 for the Wikimedia dump, zstd or LZMA for Kiwix/ZIM), and both compress multiple files at once, so inter-file redundancy should hopefully be significantly reduced.

HTML seems a bit more verbose than the Mediawiki syntax (plus the XML header for each article), but I'd be surprised if that actually accounted for a 3x difference in size.

Then again, Kiwix seems to have experimented with shared dictionary brotli compression, which supposedly yields an >2x improvement: https://github.com/openzim/libzim/issues/144

I wonder if their current zstd implementation also uses shared dictionaries. If not, that might just be the reason: If ZIM compression chunks are much smaller than the bz2 streams of the Wikimedia dumps, there would still be a lot of redundancy between chunks.

This is low-level stuff, but the new release of the backend that powers Kiwix clients, libzim 8.1.0 (changelog), now targets WebAssembly (a.k.a. WASM). This is big because it potentially brings the full powers of the Kiwix backend to Web apps such as Kiwix JS and Kiwix JS PWA/Electron. Up till now, these apps have relied on a custom JS port of parts of libzim, but it lacked full features, such as Full Text search. So, you will begin to see us integrating new features into the Web versions soon!

I'm doing my part o7

It's seriously a very interesting and useful dataset that you can do a lot of fun stuff with, if you grab one of the zims without pictures it's of very manageable size too of just a few dozen gigabytes compressed, and there are reasonably good library support in many languages.

Last point doesn't go for Java. Only one I could find for that was this <https://github.com/openzim/libzim>, it's antique and extremely poorly optimized and lacks support for newer compression schemes. I have fixed the performance and added support for zstd compression, but not published the code as it's extremely not finished and major features in the original codebase are very broken. I'll get around to sharing the code some day but right now it's basically permanently mid surgery as I've only patched so far as to get it to extract all or specific files. If anyone wants a copy of this code regardless of state, give me a holler.