Unreal Editor Low FPS
Slow viewport while working in the editor
Also known as: Unreal editor lag · Unreal viewport slow · Unreal low fps editor · UE5 editor slow · Unreal scalability settings · Unreal realtime viewport
Quick answer
A slow Unreal Engine editor viewport is usually fixed by lowering the quality the editor renders at. Open Settings > Engine Scalability Settings and choose a lower level, reduce the viewport's screen percentage, and turn off Realtime in the viewport when you are not testing lighting or animation. Switching Lumen and Virtual Shadow Maps down in the project or using a simpler view mode also helps a lot on mid-range graphics cards.
How to fix it
Work in a lighter level, hide heavy actors, and use the Unlit or Lit view mode to check content before turning on everything. Close extra viewports, since each one renders the scene. Check Stat Unit to see whether the game thread, draw thread or GPU is the limit. Keep the project on a fast drive, and avoid opening very large World Partition maps fully loaded when you only need one area.
Tools that use Unreal Editor Low FPS
See also
Lumen
UE5 dynamic global illumination
Virtual Shadow Maps
High-resolution shadows in Unreal Engine 5
World Partition
Unreal Engine 5 large-world streaming
Profiling
Measure before you optimize
CPU Bound vs GPU Bound
Which processor limits the frame rate
Shader Complexity
Viewport view of per-pixel material cost