# Different .PAK files for same packages? **URL:** \ **Category:** Multiplayer & Networking\ **Tags:** pak, unreal-engine, Multiplayer, question\ **Created:** [August 31, 2023, 12:56pm UTC](https://forums.unrealengine.com/t/different-pak-files-for-same-packages/1278732 "2023-08-31T12:56:16Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![ackyshacky](https://d1ap1mz92jnks1.cloudfront.net/user_avatar/forums.unrealengine.com/ackyshacky/32/600284_2.png) [@ackyshacky](https://forums.unrealengine.com/u/ackyshacky)\ **Post date:** [August 31, 2023, 12:56pm UTC](https://forums.unrealengine.com/t/different-pak-files-for-same-packages/1278732/1 "2023-08-31T12:56:16Z")
Hi guys, So I’m generating .PAK files for my multiplayer project (in UE 5.2). I have chunk IDs for certain folders. Now here is the weird issue… When I run back-to-back packages (without any changes in between both packages), I generate different .PAK files. So here is what happens: > Create Package A → Don’t make any changes in the project → Create Package B → .PAK files from Package A and Package B are different When I say “different”, I mean that the .PAK files from Package B are slightly different sizes from Package A. This problem basically defeats the purpose of generating .pak files for project updates. Why is that happening? ---
**Author:** ![ClockworkOcean](https://d1ap1mz92jnks1.cloudfront.net/user_avatar/forums.unrealengine.com/clockworkocean/32/1169999_2.png) [@ClockworkOcean](https://forums.unrealengine.com/u/ClockworkOcean)\ **Post date:** [August 31, 2023, 1:46pm UTC](https://forums.unrealengine.com/t/different-pak-files-for-same-packages/1278732/2 "2023-08-31T13:46:59Z")
I know you can change the PAK file ordering, > **[Packaging Projects](https://docs.unrealengine.com/4.26/en-US/Basics/Projects/Packaging/#orderingyourpakfile)** > > Packaging Unreal game projects for distribution. and I _think_ even when you don’t do that, the order isn’t deterministic. A different order could lead to slightly different file sizes. ---
**Author:** ![ackyshacky](https://d1ap1mz92jnks1.cloudfront.net/user_avatar/forums.unrealengine.com/ackyshacky/32/600284_2.png) [@ackyshacky](https://forums.unrealengine.com/u/ackyshacky)\ **Post date:** [August 31, 2023, 2:23pm UTC](https://forums.unrealengine.com/t/different-pak-files-for-same-packages/1278732/3 "2023-08-31T14:23:04Z")
Ok, interestingly, I don’t have the `GameOpenOrder.log` file in my packaged build. ---
**Author:** ![ackyshacky](https://d1ap1mz92jnks1.cloudfront.net/user_avatar/forums.unrealengine.com/ackyshacky/32/600284_2.png) [@ackyshacky](https://forums.unrealengine.com/u/ackyshacky)\ **Post date:** [August 31, 2023, 7:00pm UTC](https://forums.unrealengine.com/t/different-pak-files-for-same-packages/1278732/4 "2023-08-31T19:00:29Z")
It seems that my issue is related to this post, but no solution was ever given: > [@Patching a Project by comparing Hashes/Checksums](https://forums.unrealengine.com/t/patching-a-project-by-comparing-hashes-checksums/484013): > > Hello, I am currently working on a Updater for our project. As we are not using steam / the epic game store or any other platform that offers a patching API/System we need to implement our own solution. Out approach was to keep a list of the complete Project hierarchy including the cheksums/hashes of the files on a publicly available server and retrieve the file to compare the users local file hashes agains the currently up-to-date list on the server. Now for the problem. Building/Cooking/Pac… Any way to disable/deactivate the time stamps? ---
**Author:** ![ackyshacky](https://d1ap1mz92jnks1.cloudfront.net/user_avatar/forums.unrealengine.com/ackyshacky/32/600284_2.png) [@ackyshacky](https://forums.unrealengine.com/u/ackyshacky)\ **Post date:** [August 31, 2023, 9:41pm UTC](https://forums.unrealengine.com/t/different-pak-files-for-same-packages/1278732/5 "2023-08-31T21:41:29Z")
It seems that this is a bug on UE 5. Can someone confirm? ---
**Author:** ![ackyshacky](https://d1ap1mz92jnks1.cloudfront.net/user_avatar/forums.unrealengine.com/ackyshacky/32/600284_2.png) [@ackyshacky](https://forums.unrealengine.com/u/ackyshacky)\ **Post date:** [September 1, 2023, 8:25pm UTC](https://forums.unrealengine.com/t/different-pak-files-for-same-packages/1278732/6 "2023-09-01T20:25:35Z")
No answers for this? Does anybody currently do their own version control with .pak files and experience this issue with UE5? Because I didn’t see this happening with UE4. ---
**Author:** ![B\_REX](https://d1ap1mz92jnks1.cloudfront.net/user_avatar/forums.unrealengine.com/b_rex/32/982590_2.png) [@B\_REX](https://forums.unrealengine.com/u/B_REX)\ **Post date:** [December 14, 2023, 12:02pm UTC](https://forums.unrealengine.com/t/different-pak-files-for-same-packages/1278732/7 "2023-12-14T12:02:18Z")
Hi there. I had the same issue and just found a solution. There is no documentation to find anywhere about how the ordering works, but looking into the source code I was able find it out. So, if you don’t have a `GameOpenOrder.log` it will automatically fall back to `CookerOpenOrder.log` and `EditorOpenOrder.log`. These 2 files are changed permanently and therefore cause assets being differently ordered in paks. Even if you had a `GameOpenOrder.log` in place, it would fall back to the other ones for assets not included in the `GameOpenOrder.log`. This means if you add new stuff to your game, you will have paks again that are not deterministically. There is a way tough to specify a specific OpenOrder.log to be used and if you do this, it will ONLY use that file. In your `DefaultGame.ini` add PakOrderFileSpecs in the ProjectPackagingSettings section: ```auto [/Script/UnrealEd.ProjectPackagingSettings] PakOrderFileSpecs=(Pattern="CustomOpenOrder.log") ``` Now place a file called `CustomOpenOrder.log` in the FileOpenOrder folder next to `EditorOpenOrder.log`. The file has to exist, otherwhise the build will fail. I actually used an empty file, which basically deactivates load time optimization done by intelligent ordering inside the pak file. Honestly, I couldn’t notice a difference, but I didn’t measure the time. Now my paks are deterministic. ---
**Author:** ![SamDreams](https://d1ap1mz92jnks1.cloudfront.net/user_avatar/forums.unrealengine.com/samdreams/32/1012559_2.png) [@SamDreams](https://forums.unrealengine.com/u/SamDreams)\ **Post date:** [April 18, 2025, 8:13pm UTC](https://forums.unrealengine.com/t/different-pak-files-for-same-packages/1278732/8 "2025-04-18T20:13:30Z")
This problem is always present in Unreal 5.4.4 for me. Some pak files have different hash sometimes between 2 same packages. ---
**Author:** ![SamDreams](https://d1ap1mz92jnks1.cloudfront.net/user_avatar/forums.unrealengine.com/samdreams/32/1012559_2.png) [@SamDreams](https://forums.unrealengine.com/u/SamDreams)\ **Post date:** [April 18, 2025, 9:29pm UTC](https://forums.unrealengine.com/t/different-pak-files-for-same-packages/1278732/9 "2025-04-18T21:29:30Z")
Using the Water plugin make my game is impossible to be deterministic in 5.4.4 I think it’s fixed with the 5.5 : “Fix some cook nondeterminism bugs involving UWaterBodyMeshComponent and UAtmosphericFogComponent” > **[Unreal Engine 5.5 Release Notes | Unreal Engine 5.5 Documentation | Epic...](https://dev.epicgames.com/documentation/en-us/unreal-engine/unreal-engine-5.5-release-notes)** > > Overview of new and updated features in Unreal Engine 5.5