# Corrupted Fortnite install with the new launcher **URL:** \ **Category:** Issues and Bug Reporting\ **Tags:** open, fortnite-creative, unreal-editor-for-fortnite, epic-games-store, bug-report, fortnite\ **Created:** [October 15, 2026, 10:46am UTC](https://forums.unrealengine.com/t/corrupted-fortnite-install-with-the-new-launcher/2840742 "2026-10-15T10:46:08Z")\ **Posts on this page:** 14\ **Page:** 1
**Author:** ![giovauefn](https://d1ap1mz92jnks1.cloudfront.net/user_avatar/forums.unrealengine.com/giovauefn/32/1211471_2.png) [@giovauefn](https://forums.unrealengine.com/u/giovauefn)\ **Post date:** [October 15, 2026, 10:46am UTC](https://forums.unrealengine.com/t/corrupted-fortnite-install-with-the-new-launcher/2840742/1 "2026-10-15T10:46:08Z")
### Summary When downloading 42.40 using the new launcher, the following has happened: - I started the Fortnite update - The update stopped and UEFN update ran before Fortnite (I didn’t stop it) - I tried launching UEFN after the update, but it was crashing on launch with the following error: `Fatal error: [File:Z:\UEVFS\Root\Engine\Source\Runtime\PakFile\Private\PakFile.cpp] [Line: 377] Corrupt pak index detected on pak file: ../../../FortniteGame/Content/Paks/pakchunk70-WindowsClient.pak` - I then opened the launcher, it was telling to resume the install of UEFN although it was installed - I then realized Fortnite didn’t finish the update, so I restarted the update, which somehow was 70gb - After the download, Fortnite started repairing and installing processes like 5 times in a row, with different sizes, until it installed - Trying to launch Fortnite gave me the same error in game, invalid pak, although it didn’t crash - I then tried uninstalling the Launcher since I wanted to go back to the old one - Uninstalling did nothing for some minutes. Until I realized the entire Epic Games folder in C:\Program Files\Epic Games was gone. All games were removed, along with the launcher. ### Please select what you are reporting on: Unreal Editor for Fortnite ### What Type of Bug are you experiencing? Other ### Steps to Reproduce - ### Expected Result Pak wasn’t corrupted ### Observed Result Pak was corrupted ### Platform(s) Windows ### Additional Notes I installed the old launcher and reinstalled Fortnite and UEFN. They both work fine now, but this could help fixing bugs with the new launcher. ---
**Author:** ![iiiSAndman](https://d1ap1mz92jnks1.cloudfront.net/user_avatar/forums.unrealengine.com/iiisandman/32/891514_2.png) [@iiiSAndman](https://forums.unrealengine.com/u/iiiSAndman)\ **Post date:** [October 15, 2026, 10:50am UTC](https://forums.unrealengine.com/t/corrupted-fortnite-install-with-the-new-launcher/2840742/3 "2026-10-15T10:50:22Z")
I’ve had a similar’ish issue today using the new launcher. My steps though were: - My new launcher didn’t show any signs of a new update anywhere, even when clicking manage on Fortnite/UEFN - I then decided to download the original EGL and deleted the new one - Before opening the old launcher again, I noticed another dev said the new launcher update worked for them, so I decided to delete the original EGL and download the new launcher again - Upon opening the new launcher, my Fortnite/UEFN said INSTALL instead of update… So now I’m stuck with potentially a 20+ hour wait time to download these programs that were fine before ---
**Author:** ![Flak](https://d1ap1mz92jnks1.cloudfront.net/user_avatar/forums.unrealengine.com/flak/32/769441_2.png) [@Flak](https://forums.unrealengine.com/u/Flak)\ **Post date:** [October 15, 2026, 11:02am UTC](https://forums.unrealengine.com/t/corrupted-fortnite-install-with-the-new-launcher/2840742/4 "2026-10-15T11:02:12Z")
Thanks for flagging, getting someone to take a look. ---
**Author:** ![Flak](https://d1ap1mz92jnks1.cloudfront.net/user_avatar/forums.unrealengine.com/flak/32/769441_2.png) [@Flak](https://forums.unrealengine.com/u/Flak)\ **Post date:** [October 15, 2026, 11:19am UTC](https://forums.unrealengine.com/t/corrupted-fortnite-install-with-the-new-launcher/2840742/5 "2026-10-15T11:19:30Z")
@giovauefn @iiiSAndman Are you getting any errors? If so, what is the error code? ---
**Author:** ![Flak](https://d1ap1mz92jnks1.cloudfront.net/user_avatar/forums.unrealengine.com/flak/32/769441_2.png) [@Flak](https://forums.unrealengine.com/u/Flak)\ **Post date:** [October 15, 2026, 11:24am UTC](https://forums.unrealengine.com/t/corrupted-fortnite-install-with-the-new-launcher/2840742/6 "2026-10-15T11:24:14Z")
Could we also get your launcher logs? ![image](https://d3kjluh73b9h9o.cloudfront.net/original/4X/c/b/2/cb229fc6b14552b52d23206b2f260603b0ad6054.png) ---
**Author:** ![Velocity\_Zero](https://d1ap1mz92jnks1.cloudfront.net/user_avatar/forums.unrealengine.com/velocity_zero/32/1036910_2.png) [@Velocity\_Zero](https://forums.unrealengine.com/u/Velocity_Zero)\ **Post date:** [October 15, 2026, 11:30am UTC](https://forums.unrealengine.com/t/corrupted-fortnite-install-with-the-new-launcher/2840742/7 "2026-10-15T11:30:45Z")
Claude fixed it for me, you’ll find below its summary. * * * **UEFN 42.40 crashes at startup: “Corrupt pak index detected” on a leftover 42.30 pak (pakchunk70-WindowsClient.pak)** **Versions** - UEFN: ++Fortnite+Release-42.40-CL-59247843 - Fortnite: ++Fortnite+Release-42.40-CL-59086525 (updated from 42.30, CL-58813929) - Epic Games Launcher 20.3.5, Windows 10 **Symptom** UEFN crashes immediately on launch, before any project opens. The crash log ends with: ```auto Corrupt pak PrimaryIndex detected! Filename: ../../../FortniteGame/Content/Paks/pakchunk70-WindowsClient.pak Encrypted: 1 Total Size: 421212 Index Offset: 403830 Index Size: 1040 Stored Index Hash: 5885F32C751D18AA265150175A4BA741F6AAA4D6 Computed Index Hash: A3301133EE1EA6A50FCA32F3B9553EC8CF0CD5EF Fatal error: [File:.../Runtime/PakFile/Private/PakFile.cpp] [Line: 377] Corrupt pak index detected on pak file: ../../../FortniteGame/Content/Paks/pakchunk70-WindowsClient.pak ``` **Cause** The pak is not corrupt. It is left over from 42.30: - pakchunk70-WindowsClient (.pak, .sig, .ucas, .utoc) is dated from the 42.30 release. - It is not listed in either 42.40 install manifest (Fortnite or UEFN). - It uses the main key, and the 42.40 main key opens every other main-key pak in the folder but not this one, so it is still encrypted with the 42.30 key. - UEFN mounts every pak in the Paks folder at startup, fails to decrypt this one, reports it as corrupt and stops with a fatal error. Ten more 42.30 pak sets were also left behind and are not in either 42.40 manifest: pakchunk1001, 1002, 1003, 1004, 1006, 1007, 1013, 1016, 1022 and 1023 (about 220 MB). They use their own keys, so they did not crash UEFN, but they are dead files. Verifying both Fortnite and UEFN in the launcher completed successfully but did not remove any of these files, because Verify only checks files that are in the manifest. Background: this install went through several failed update attempts first (the IS-UP-IZ04 “Invalid InstallTags” launcher issue, since fixed by a launcher update), including a fresh reinstall over the existing install folder, so I cannot say which step left the files behind. **Workaround (confirmed)** Close UEFN and Fortnite, then move the leftover files out of the Paks folder (moved, not deleted, so it can be undone). In Command Prompt, for the default install folder: ```bat mkdir "%USERPROFILE%\Fortnite-42.30-leftovers\Paks" for %n in (70 1001 1002 1003 1004 1006 1007 1013 1016 1022 1023) do @for %e in (pak sig ucas utoc) do @move "C:\Program Files\Epic Games\Fortnite\FortniteGame\Content\Paks\pakchunk%n-WindowsClient.%e" "%USERPROFILE%\Fortnite-42.30-leftovers\Paks\" dir /b "%USERPROFILE%\Fortnite-42.30-leftovers\Paks" | find /c /v "" ``` The last line should print 44. If it reports “Access is denied”, run Command Prompt as administrator. The chunk numbers are the ones left over on my install; on another machine, pakchunk70 is the one named in the crash log, and other leftovers may differ. To undo: ```bat move "%USERPROFILE%\Fortnite-42.30-leftovers\Paks\*" "C:\Program Files\Epic Games\Fortnite\FortniteGame\Content\Paks\" ``` After moving the files, UEFN 42.40 starts normally. **Requests** 1. Have updates and repairs remove pak files that are no longer in the build’s manifest. 2. Have Verify report (or offer to remove) extra pak files in the Paks folder. 3. When a pak that is not part of the current build cannot be decrypted, skip it with a warning instead of a fatal “corrupt pak” error, or at least name the file and suggest removing it. ---
**Author:** ![giovauefn](https://d1ap1mz92jnks1.cloudfront.net/user_avatar/forums.unrealengine.com/giovauefn/32/1211471_2.png) [@giovauefn](https://forums.unrealengine.com/u/giovauefn)\ **Post date:** [October 15, 2026, 1:37pm UTC](https://forums.unrealengine.com/t/corrupted-fortnite-install-with-the-new-launcher/2840742/8 "2026-10-15T13:37:23Z")
@Flak the error I was getting was: `Fatal error: [File:Z:\UEVFS\Root\Engine\Source\Runtime\PakFile\Private\PakFile.cpp] [Line: 377] Corrupt pak index detected on pak file: ../../../FortniteGame/Content/Paks/pakchunk60-WindowsClient.pak` and then at some point the same one, for pakchunk70. As for the logs, I don’t have the new launcher anymore, but I still should have them in appdata. Is the path for the logs `AppData\Local\EpicGamesLauncher\Saved\Logs`? If so, I’ll DM them to you on discord. ---
**Author:** ![iiiSAndman](https://d1ap1mz92jnks1.cloudfront.net/user_avatar/forums.unrealengine.com/iiisandman/32/891514_2.png) [@iiiSAndman](https://forums.unrealengine.com/u/iiiSAndman)\ **Post date:** [October 15, 2026, 2:23pm UTC](https://forums.unrealengine.com/t/corrupted-fortnite-install-with-the-new-launcher/2840742/9 "2026-10-15T14:23:19Z")
Sent my logs to Daniel. I reinstalled Fortnite/UEFN, but UEFN is still crashing immediately on launch. Same error that Giova mentioned ---
**Author:** ![Flak](https://d1ap1mz92jnks1.cloudfront.net/user_avatar/forums.unrealengine.com/flak/32/769441_2.png) [@Flak](https://forums.unrealengine.com/u/Flak)\ **Post date:** [October 15, 2026, 2:23pm UTC](https://forums.unrealengine.com/t/corrupted-fortnite-install-with-the-new-launcher/2840742/10 "2026-10-15T14:23:40Z")
Thank you, Sandman! ---
**Author:** ![Bug-Reporter](https://d1ap1mz92jnks1.cloudfront.net/user_avatar/forums.unrealengine.com/bug-reporter/32/997076_2.png) [@Bug-Reporter](https://forums.unrealengine.com/u/Bug-Reporter)\ **Post date:** [October 15, 2026, 3:01pm UTC](https://forums.unrealengine.com/t/corrupted-fortnite-install-with-the-new-launcher/2840742/11 "2026-10-15T15:01:03Z")
The status of FORT-1173159 changed to ‘Needs Triage’. We are routing this to the appropriate team for investigation. ---
**Author:** ![TimSkijwalker](https://d1ap1mz92jnks1.cloudfront.net/user_avatar/forums.unrealengine.com/timskijwalker/32/1194705_2.png) [@TimSkijwalker](https://forums.unrealengine.com/u/TimSkijwalker)\ **Post date:** [October 16, 2026, 6:55pm UTC](https://forums.unrealengine.com/t/corrupted-fortnite-install-with-the-new-launcher/2840742/12 "2026-10-16T18:55:18Z")
I had the same issue, I deleted the pak file and re-downloaded it with fortnite verify and now it does work. EDIT: Update, UEFN works but fortnite doesnt launch anymore with another pak error… rip ---
**Author:** ![Steven.Isaacs](https://d1ap1mz92jnks1.cloudfront.net/user_avatar/forums.unrealengine.com/steven.isaacs/32/1087802_2.png) [@Steven.Isaacs](https://forums.unrealengine.com/u/Steven.Isaacs)\ **Post date:** [October 16, 2026, 8:13pm UTC](https://forums.unrealengine.com/t/corrupted-fortnite-install-with-the-new-launcher/2840742/13 "2026-10-16T20:13:55Z")
I’m getting a similar error and can’t run UEFN. It crashes before it opens either when I try to load a project or just run UEFN, Below is my screen shot. I even changed the name of my Fortnite Projects folder hoping that it was because of corrupt files in there. ![image](https://d3kjluh73b9h9o.cloudfront.net/original/4X/3/0/6/306faf05a62cd2bde21fe231056c3bb0e25376d6.png) ---
**Author:** ![Jimbohalo10](https://d1ap1mz92jnks1.cloudfront.net/user_avatar/forums.unrealengine.com/jimbohalo10/32/961440_2.png) [@Jimbohalo10](https://forums.unrealengine.com/u/Jimbohalo10)\ **Post date:** [October 17, 2026, 9:52am UTC](https://forums.unrealengine.com/t/corrupted-fortnite-install-with-the-new-launcher/2840742/14 "2026-10-17T09:52:12Z")
hi @Steven.Isaacs , Please look at the workaround which have allowed me to load TWO pc with 42.40 successfully. [Unable to launch fortnite through UEFN after installing the new EGL or latest update - General / Issues and Bug Reporting - Epic Developer Community Forums](https://forums.unrealengine.com/t/unable-to-launch-fortnite-through-uefn-after-installing-the-new-egl-or-latest-update/2841564/2) You may be able to complete the install with the workaround using verify [How to Verify UEFN/Fortnite](https://forums.unrealengine.com/t/urc-exe-and-urc-dll-get-flagged-as-malware-from-microsoft-defender/1802519/5) If that fails the quickest way would be to uninstall UEFN/Fortnite using the workaround Launcher. Restart the PC and install UEFN/Fortnite as normal Thanks ---
**Author:** ![\_L\_U\_C\_K\_Y](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@\_L\_U\_C\_K\_Y](https://forums.unrealengine.com/u/_L_U_C_K_Y)\ **Post date:** [October 17, 2026, 1:35pm UTC](https://forums.unrealengine.com/t/corrupted-fortnite-install-with-the-new-launcher/2840742/15 "2026-10-17T13:35:45Z")
I have the same isue and i think it is just a bug i think epic will fix it soon i hope