When working in Unreal Engine 5 with the RHI set to DirectX 12, I experience severe editor lag. The problem becomes critical when any child window (e.g., Blueprints, Material Editor, or any asset) is moved to a second monitor. At this point, the FPS in both the main viewport and the child window drops dramatically, making work impossible.
Even when working on a single monitor, the editor UI FPS remains low and unstable, as if it’s artificially locked to a low framerate.
Key Diagnostic: DX12 vs. Vulkan
DirectX 12 (The Problem): Severe editor lag, UI stutter, and critical FPS drops with multiple monitors.
Vulkan (The “Fix”): When switching the project’s RHI to Vulkan, all editor performance issues completely disappear. The UI, viewport, and multi-monitor workflow become perfectly smooth.
My Goal: I need to keep using DirectX 12 because the performance of the final compiled game (the shipped build) is significantly better on DX12 than it is on Vulkan in my project.
This problem persists despite all my attempts to isolate it:
All UE5 Versions: The issue is present in every version of Unreal Engine 5 (from 5.0 to 5.6).
Empty Scene: The lag occurs even in a completely empty, new project/scene.
Lumen: Disabling Lumen does not solve the problem.
Virtual Shadow Maps (VSM): Disabling VSM does not solve the problem.
Scalability Settings: Changing the Engine Scalability Settings (from Low to Epic) has no effect on the UI/editor lag.
GPU Drivers: I am on version 581.57. Updating to newer drivers (or rolling back to older ones) has no impact on this issue.
The Question
Are there any known solutions, workarounds, or settings (in Windows, Nvidia Control Panel, or UE5) to resolve this editor-specific performance issue on DirectX 12?
How can I achieve a smooth editor workflow on DX12, especially with a dual-monitor setup, without having to switch to Vulkan for development?
Partial Solution Found! (MSI Afterburner / RTSS is the culprit)
The main culprit for the severe stutter and FPS crash was MSI Afterburner, or more specifically, RivaTuner Statistics Server (RTSS).
The “Why”
The Unreal Engine 5 editor is a very complex application that uses DirectX 12 extensively for its UI. It seems RTSS (which handles the Afterburner OSD) tries to “hook into” or “inject” itself into every single UI element.
This was causing:
The insane lag when just hovering over buttons.
The catastrophic FPS crash when moving a window to a second monitor.
The Solution (If you need Afterburner for Undervolting)
This fix lets you keep MSI Afterburner running (which I need for my GPU undervolt), but stops RTSS from interfering with the editor:
Open RivaTuner Statistics Server (RTSS). (It’s the app that runs alongside Afterburner, check your system tray).
Click the green “Add” button and create a new profile for the UE5 editor. (Find your ...UE_5.x\Engine\Binaries\Win64\UE5Editor.exe).
With the UE5Editor.exe profile selected, set “Application detection level” to “None”.
(Optional) If that doesn’t work, you can try setting the “Global” profile’s “Application detection level” to “None” as well, but the specific profile for the editor should be enough.
The Results (Why it’s only 50% solved)
This fix made a night-and-day difference, but it’s not perfect.
What’s 100% FIXED:
The severe FPS drop and stutter when just hovering the mouse over UI elements is COMPLETELY GONE. The editor UI is now perfectly smooth to interact with.
What’s PARTIALLY FIXED (The Remaining Problem):
The dual-monitor problem is much, much better, but not fully resolved.
Before: Moving a Blueprint window to my second monitor dropped my FPS from ~120 down to ~20 FPS.
After: Now, doing the same thing drops my FPS from ~120 down to ~80 FPS.
This is a massive improvement, and the editor is usable again. However, an 80 FPS cap is still a significant performance hit, and I would like to recover those lost frames.
I already checked my NVIDIA settings, and G-Sync is fully disabled, so that is not the cause of the remaining 80 FPS drop. I am still investigating how to fix this final part of the problem.
BONUS TIP: I also recommend disabling “Hardware-accelerated GPU scheduling” (HAGS) in Windows Settings (under Display > Graphics > Default graphics settings), as this can also cause conflicts with professional DX12 applications and disabling it can gain back a few more frames.
Hope this helps anyone else pulling their hair out over the UI stutter! I’ll post another update if I find a fix for the remaining 120 → 80 FPS drop.
You could try lowering the priority of RTSS and afterburner.
Open task manager and go to the details tab.
Find afterburner and rtss and right click them, then “set priority” => below normal.
You could try raising the editor’s priority as a test to see if it’s faster (though choosing the highest priority might be a bad idea)
Also make sure your power plan is set to performance in windows. This can impact the performance by a lot.
[SOLVED] Final Update & Root Cause of Remaining FPS Drop
Hello everyone,
After a lot of testing, I can finally confirm the root cause of all the performance issues. I am marking this thread as “solved” because the original critical bugs are fixed, and the remaining issue is a known platform limitation.
Here is the final summary:
Part 1: The Critical Bug (SOLVED)
The severe UI stutter (lagging when hovering over buttons) and the catastrophic FPS drop (120 → 20 FPS) was caused by MSI Afterburner / RivaTuner Statistics Server (RTSS).
Solution: Adding UE5Editor.exe to RTSS and setting its “Application detection level” to “None” fixed this 100%. The editor is now perfectly smooth to interact with.
Part 2: The Remaining 120 → 80 FPS Drop (The “Why”)
After fixing the RTSS bug, I still had a performance drop from ~120 FPS down to ~80 FPS when moving a window to my second monitor.
I have now confirmed this is caused by my monitors having extremely different refresh rates (180Hz + 60Hz).
Here’s the logic:
The Windows Desktop Window Manager (DWM) is the service responsible for drawing all application windows.
When a DX12 application (like the UE5 editor) is running in windowed mode and is “stretched” across two monitors with vastly different refresh rates (180Hz vs 60Hz), the DWM struggles to synchronize them.
It cannot run both at their native speeds. Instead of dropping to 60Hz, it seems to be forcing the application into a “compromise” state, which in my case results in a cap of around 80 FPS.
I even came up with a simple “formula” that describes the symptom well: (My 120 FPS + 60Hz Monitor) / 2 = 90 FPS. Minus the overhead of the second window, this lands exactly at the ~80 FPS I’m seeing. While not technically how DWM calculates it, this perfectly illustrates the “averaging” effect.
Conclusion: The drop to 20 FPS was a software bug (RTSS). The remaining drop to 80 FPS is a platform limitation of Windows/DWM/DX12 handling disparate refresh rates.
Since an 80 FPS cap is perfectly usable for an editor (compared to 20!), and the cause is now known, I consider this investigation closed.
Thank you to everyone who offered suggestions. I hope this thread helps others who are debugging similar issues!
Problem Summary
Key Diagnostic: DX12 vs. Vulkan
My System Specifications
The Question