Using UnrealPak how do you set up a Response file?

Hi all,
I’m new to UnrealPak and trying to find documentation on how to set up the response file for a mod.
D:\Win64\UnrealPak.exe (PathTo.pak) -Create=(PathToSourceFolder)
Puts the files I want inside a pak file, however they are not listed under sub-directories inside it.
How would one go about writing a response file that creates sub-directories inside the pak and puts files inside of them?
Much appreciated!

Edit: I was kindly informed that it is as simple as using:

“C:\Mod\newtry\Engine*." "…\Engine*.
“C:\Mod\newtry(Foldername)*." "…(Foldername)*.

Works perfectly, thank you very much!

Thank you for Sharing. Can you give a little more information what you do? Do you use it to Make a Mod?

Thanks for the interest!
We are currently figuring out how to mod Battlefleet Gothic 2 (with the permission of the devs, Unreal version 4.18). Most of the key files are stored inside a 40GB pak file, thus making modding difficult.
One clever guy figured out how to get the game to load up an additional pak file on launch, in which you can place modded files.
I’ve just been checking my pak creation process, as the game will only accept certain kinds of files and hasn’t been loading mine.

Most of the files inside the pak have already been ‘cooked’, making it doubly difficult to change.

We would love to hear if anyone has any insights into modding Cooked Unreal paks, it has proven somewhat challenging!

it makes sens that is not easy to modify or use cooked assets…so not everybody is stealing and piracing your stuff…if you have the permission of the devs, they can/need to give you the original files.
cooking is a process where the original file is “converted” into platform specific assets - so it can’t be reverted (as far as I know). But you could create the folder Structure in an empty UE Project, add your custom Iconfiles/Images in ue, cook them, and than exchange the .pak as you already know how to do - I guess this would work

I’ve got the pak loading in correctly now.
However it still doesn’t like the files I’m putting in it, giving out errors such as


Any insight into how to correct these issues would be much appreciated!

Edit, image didn’t display right.


Pak is working fine, just unsure how to format the items being put into it : (

Maybe I can help you, but I don’t know exactly how the work is going.

There are several ways to use custom assets at runtime.

It depends on “Mount Order” of pak. If a resource with the same path resides in two packs, the resources in the higher order are loaded.

The first way, you can cook specific assets, make “Suitable” response files, make a pak that will overwrite origin assets, and mount it with higher mount order.
If you can handle C++, you can use custom order that you want by modify engine’s source .
But if you can’t handle C++ or don’t want to modify engine’s code, you can use rule of pak file name for unreal patch system.

The second way, you can use unreal patch system itself.
You can make “diff-pak” with using “project launcher” in unreal editor, and place it in pak file path.
This “diff-pak” will be named “*_P.pak”, and It will be mounted with higher order than origin pak.

If you want to use the first way, ask me questions by reply. But I recommend the second way, which can be known by through the Unreal document.

Thanks for the insight!
Before coming back here I finally managed to crack it, the game (Battlefleet Gothic 2) can load up multiple Pak files at once provided they have the same name (just in different subfolders inside the pak folder).
Using Unreal I can also load and ‘cook’ assets to be placed inside the custom paks (which can overwrite content from the original pak).

The patch option sounds quite intriguing, I’ll look into it.
I’ve manged to load custom models, images and audio into the game. Blueprint files however are proving more of a challenge as I can’t just create my own, and hex editing the existing files is a minefield. I was recommended the 010 Editor which can apparently do quite advanced stuff with previously in-accessible files like these. (010 Editor - Pro Text/Hex Editor | Edit 200+ Formats | Fast & Powerful | Reverse Engineering)

There’s clearly usable and editable data there, I just don’t have a clue how to edit it without screwing up the file.

In regards to the 010 editor, I also got sent this:
“Go to the UE4 source code, find the serialization code, and punch it into a template in 010. Repeat that until you have coverage of the stuff you need and you can edit what you want”
I can’t find much documentation on this, does anyone know where one might find this?

I’m sorry for my late checking the comments.

Because of my lack knowledge of game-modding, I don’t know why you need to use 010 editor. I think there are better ways than that. Tell me what situation you are in and what you want to achieve.

Thanks Wanja!
For whatever reason my posts here take up to 2 days to appear (some weird moderation thing for new members?)
Our predicament:
-Most of the BFG2 Files are relatively easy to mod. However blueprint and some other files are not easy to edit as we can’t reverse engineer them back into unreal engine (like you can with the models and audio).
As we can’t uncook them (they reside inside the 40GB pak), the only option I know of is to Hex-Edit them (directly edit the raw code), however to change the size of the file you need to find the header which lists the size and edit it, despite the values it lists being very difficult to understand and change.
This is pretty difficult for us, however I know of one person who has done this succesfully.

Essentially we want to figure out how to edit/create these files.
The content of these files is mainly listing assest names and what goes where, firing arcs etc.
The files we are trying to edit can be downloaded here:
From the extracted Pak each file has a .uasset (contains the file size line) and a .uexp (content and values)

I have had great success with importing custom models into the game though!

I’m sorry that my reply seems to be repeated.

There is a part in the reply that you want to edit the blueprint… Does It mean that you want to modify “logic” of this game, not “resources”?

If you just want to modify resources, you just use modified asset with path that same with origin asset’s one, you don’t need to fix pak file by 010 editor, but just do place your pak file(ends with “_P.pak”) in the same directory as origin one.

But if you want to modify logic, I don’t know how it is possible.

We can add files to the custom pak and load it without issue, It’s just certain files we’ve extracted from the pak are difficult to edit. They are Blueprints created by Unreal engine, but have been cooked and thus cannot be loaded back into Unreal for editing
(Thus using a hex editor to try and change the data inside them).

We know that it can be done as someone has already done so, but replicating it is pretty hard XD

Thanks for your support!


I’ve manged to load custom models, images and audio into the game

Did you manage to override images for example, ie your image over the original ones with the help of a _p.pak file?