Why is 4.00 Hotfix so huge.... 49 GB... Already had 4.00 installed.

This is really odd few days ago I thought Galaxy had updated my unmodded Witcher 3 with a 6mb Patch, all the time since the hotfix was released Galaxy would not download a patch when I clicked check for update.

Today it wants to download 51gb and the offline patch installer (~1.8gb) does not work for me....

same patch on steam seems to be just over 2gb, it's insane that there's no incremental patching on their own launcher

Mildly interesting:
Just tried to install the hotfix again (offline) and the installer told me that I already have it installed so Galaxy patched it with a 6mb download.

Now the hotfix became a new "normal" build (abstracted from the namingconvention) and Galaxy wants to download 51gb.
The new offline patch installer is a bit over 2gb. Offline patch installer just finished downloading, here is hoping it wont fail like the hotfix...

The offliner installer worked today and for me given the release history I gave it a 50:50 chance of success ;)

GoG Patcher says it needs about 19gig of freespace to install the hotfix

This can be. every file being changed, even by only 10 KB, is backuped as a whole until the updater confirms the success. Then those files are removed again, or rolled back on failure. So these 19GB are only temporary.

How did you install the hotfix update from offline installer? I can only find untill 1.32 at gog.com.

Games > Witcher 3 Complete Edition > List on the left:
Patch (4.00_Hotfix to Build_66291Change_5524291)

The real answer: Because the way some games are packed, even if you only have to download 1-2GB of files for minor changes, the drive has to re-write the entire pack of whatever file that change was made to. So if you need to make a 1mb change to a 4gb file the drive has to re-write the full 4gb... So even though the download size for me was very small, almost the whole folder was re-written in the hotfix.

The fun answer: Because the state of the game was complete trash after 4.0.0 and they needed to patch 50GB of the 60GB game to fix it. /s

Yeah, but that does not explain needing to actually download 49 GB. I can understand, that update requires enough free space for full install, so that new version can be made complete before switching over.... So that until the last moment existing install is still whole.
But that does not need huge download, unless there were huge changes in data. because 1 MB batch to 4GB file can still take 4 GB file from existing install....

If it just downloads the patch and applies it locally to the files, this is true. If however only a sync from the server side files to the client side files is done, than every file, that got changed somehow is downloaded as a whole. The process of sync has the benefit of not relying on which version is on the client. you check the CRC of every file and on difference, you replace it. This way you also fix damaged files on the client and other inconsistencies like broken updates. It's less hassle dealing with many possibles things that can go wrong in exchange for more download bandthwith.

That's weird, it doesn't show me that. The last item is Patch (1.31 to 1.32).