Hello there. Hope you're all fine in those troubled times

I'm trying to backup some of my GOG Offline installers, but it seems I can't reduce their size through compression enough.
They're encryped and I heard that because of that any compression tools can't compress them really well because of algorithm reasons.

Any tips on best methods for the compression of GOG Offline installers?
Do you compress your games installers or just backup them how they are?
If yes, how you compress your offline installers?

The game data in the installers is already compressed, so there is not much point in trying to compress it any more. Just back up the installers as they are.

The install files are already compressed. Just look ar your games in your library, or any game's page on the site: thr games require twice as much space as the the install files.
Actually you'll probably end up with slightly bigger files than the originals, because compressing them again will only add let's call it "metadata".

Thanks for the answers.

Isn't possible to compress them even more?

Hm... I've made tests before and I got good results using p7zip compressing game files after they were installed, but to install each of them just to compress them again would be troublesome, that's why I'm asking if there's another way of doing this with the installers.

But welp... Thanks.

Yes, that is the way. Better compression can be used, but you need to create your own installers for it, compressing the game files and then also adding the scripts for what they put in the user directory and registry (unless you want to do that manually). Remember that there was a discussion showing how much better the compression can be at one point, but it requires going through all that trouble for each game, and again whenever it gets updated...

Yeh... It doesn't sound practical. :|

What rubbish! GOG uses very poor compression in their installers, not to mention they bundle everything into them. Simply compare GOGs 60gb installer for cyberpunk against “other” installers at 50% smaller sizes. Taking some time and effort from GOGs side to provide proper decently compiled installers is a big issue with the site:
https://www.gog.com/forum/general/provide_a_full_and_complete_changelogged_download_system Further to my post above, if you seriously want to save some space and are prepared to put some work in, then yes you can reduce the size, something which GOG should have been doing. It’s a bit game specific, but in essence:
Use and extractor for your current GOG installer to get all the files out, then identify what you need (endless copies of c++ installers, or dosbox installers etc. could go), take out language packs/videos you don’t need, then recompress at highest compression.
The rate of saving however will be dependent on the game, a 1mb installer for a game from 1980’s isn’t going to save you anything for the work involved. For the large games here however they can save you a fair bit.

And I can understand it being an issue, games are becoming huge >100gb, so any storage saving now is becoming useful.

Thank you for the link and explanation nightcraw1er.

The reason you can no doubt gain a size benefit that way, is that not everything inside an installer gets installed (i.e. other language files, and external files that may already exist on your system, etc). So when you are compressing the game folder after installation, you could be compressing a much smaller source.

Not with the current technology. If you had the uncompressed stream you could recompress that, but it isn't an option.

Example, say you got a tar.gz file, you could do: zcat archive.tar.gz | xz -9 -f >archive.tar.xz, which will give better compression (hopefully).

Compression is one of two ways, lossless (Look for identical patterns and reference them, or use dictionaries of more often used blocks in fewer bits) or Lossy (Take an image, lower the quality which looks very similar to what the original was but at a fraction of the size).


However since GoG is also selling more Visual Novels and games, there's actually better ways to compress them, generally doing better optimization on images (Jpegoptim) or with RenPy games converting images to WebP but leaving the original filenames regardless the type they are. However the installers themselves won't help with this.

No no. Let's be honest and truthful (no matter what), it is technologically possible for an advanced user. Let's see, every chunk of an installer is compressed by ZLIB and then the chunk's names are hashed/randomized and put into another container with another ZLIB compression, then the container is split into BINs (as "MadeUpName556" noted). To minify, reverse the operation, save the hash/random map, apply LZIP, BZIP2 or any other compression, save the file and the map, and done. To use the minified, the application must re-do the process backwards. InnoExtract can do the 1st part, reversing, might be used as "a guide" on looking how exactly the process goes for extraction.

Is it done by anyone? No, not yet. Is it possible? Yes, absolutely is.

This annoys me.
So much space is wasted on my NAS because the installers contains the files for all languages a game have been relase in.
Like you mentioned, the Cyberpunk 2077 installer is around ~100GB while the installed size lands at around 60GB. That's 40GB wasted and that's not taking in the compression of the installer into account. So it's more than 40GB wasted.