UEFN 40.00 is easily 300% slower than previous version

Summary

I don’t know how to “repro” this outside of the experience I am having since 40.00 in comparison to the previous version working on a single project. While before it would take a long time (easily 3 mins to push just verse changes), now takes up to 8 or 9 mins to push just verse changes.

Also, UEFN is now consuming pretty much all my computer resources making the rest of my apps running (including fortnite itself) to be laggy and slow and unresponsive.

To put in layman’s terms at this point, UEFN is an absolute PIG on resources of CPU and memory for no discernible increase in functionality or improvements itself. It’s as if there is some kind of horrible loop running, or a miscalculation of how memory is used within it. Creating and building in UEFN has become almost a miserable experience on my machine that has 16GB RTX4090 with a 13gen I9 cpu and 32 GB or memory.

This is unacceptable at this point and I really hope that there is some kind of change in the UEFN dev team to make this software BETTER instead of successively worse each iteration as we spend hours per day just simply waiting to push a small change.

Please select what you are reporting on:

Unreal Editor for Fortnite

What Type of Bug are you experiencing?

Memory

Steps to Reproduce

Open a large project and work on it

Expected Result

Should be quicker and leaner and more efficient

Observed Result

Is a bloated mess of software that sucks up all resources on the computer

Platform(s)

PC

Hello @GraemeBB

I come to you with requests for assistance from the team. :wink:

Could you please give us an island code for one of your large projects so we can start investigating? Also, if we could get both your client and editor logs after you open one of the projects where this is happening.

Feel free to send here or on Discord.

Thank you, as always!

The island code is 9664-2937-0308. I’ll see about getting logs too.

Thank you!

I second that.

It can take twice or thrice as long to push Verse changes since this new version came out.

Also the editor has become a huge memory hog, though it does seem to somewhat fix itself after 15 minutes or so.

1 Like

Just to follow up on this, I sent logs to you in discord and as of yesterday UEFN won’t even close properly anymore, I always have to force close or it crashes (which I send logs each time too). UEFN is exponentially worse since 40.00 in performance and stability.

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Thank you, Graeme, will let the team know.

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FORT-1079191 has been added to our ‘To Do’ list. Someone’s been assigned this task.

If I may, this isn’t just a problem on large projects - it’s on all projects, and this issue has been around (and worsening) for the better half of a year, if not longer.

Even the home screen of UEFN often takes up most of my PC’s available memory (32GB). It’s become impossible to launch a memory calculation, much less playtest, without my whole PC seizing up and Fortnite running at a crisp slideshow of 10FPS or lower, and sometimes it still even does that without having Fortnite, or anything else, open.

I’ve also heard reports of people with 64 and 128gb of RAM having the same issue - UEFN taking up 90% of their available memory, if not more, despite not actually needing it or improving performance. This seems like a pretty serious internal issue.

@Flak

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hi @GraemeBB @Flak

There always seems to be two copies of UEFN 40.00 running when hovering over taskbar icon

Fortnite was running the island listed above at the same time as starting UEFN 40.00

This possibly caused Fortnite island to crash.

the Fortnite crashed log is here

FortniteGame.log (4.6 MB)

see line 33200

[2026.03.26-22.59.37:111][701]LogAudioMixer: Warning: AudioMixerPlatformInterface Timeout [ 5 Seconds] waiting for h/w. InstanceID=1
[2026.03.26-22.59.37:111][701]LogRendererCore: Error: GameThread timed out waiting for RenderThread after 40.01 seconds:
[2026.03.26-22.59.37:113][701]LogRendererCore: Error: 0x00007ffb3f141b14 ntdll.dll!UnknownFunction
[2026.03.26-22.59.37:113][701]LogRendererCore: Error: 0x00007ffb3b8fb1bf KERNELBASE.dll!UnknownFunction
[2026.03.26-22.59.37:113][701]LogRendererCore: Error: 0x00007ff67433fbf1 FortniteClient-Win64-Shipping.exe!UnknownFunction
[2026.03.26-22.59.37:113][701]

There is NOT an actually UE 5 crash just several crashed process in the logs

There is a popup about memory squezze and it moves position which proves two versions are running on Windows 11 with the latest patches.

My graphics card is an intel UHD laptop card

UEFN does not crash and clicking the red X one any version bring the PC back to running one version of Uefn

1 Like

This has been a problem for me too. The projects I work on reach the map’s memory limit, with hundreds of custom props and hundreds of actors. It’s impossible for me to use any of the “push” features; I have to reopen the experience through the lobby because UEFN or Fortnite will definitely crash. I’m using 48GB of RAM, a Ryzen 7 5700X, a 5060 Ti, and an NVMe 2.0 SSD. Also using the “Close Project” button or the X in the top corner of the window doesn’t work either; the application may close, but the task will always remain in the background on your PC, consuming all your memory. That’s why I added “End Task” directly to the application’s taskbar, that’s the only way to truly close the editor.

The good news is that I’m really excited about the changes Epic announced regarding the the coking process and other things

3 Likes

From 40.10 this problem is even worse, UEFN and Fortnite suck up even more memory and CPU than before making every other program almost unusable at times. I sure hope this gets resolved very very soon….

same here!

I noticed if you turn on stats for UEFN to show framerate and memory usage, it will balloon in size even if you have a bare minimum project open. The Objects in memory seem to always stay in memory if if you have closed out a previous project.