Quick answer: some lights or objects use baked (static) lighting that hasn’t been calculated yet.
- Using baked lighting on purpose? Click Build > Build Lighting Only and wait for it to finish.
- Using Lumen (the UE5 default)? You don’t need baked lighting. Set your lights to Movable, or turn off Allow Static Lighting in Project Settings and restart.
- Just one level? In World Settings, tick Force No Precomputed Lighting.
The message
LIGHTING NEEDS TO BE REBUILT (12 unbuilt object(s))
It shows in red in the viewport and in Play mode. Shadows and light may look wrong or flat until it’s fixed.
Why it appears
Lights set to Static or Stationary use lightmaps that Unreal bakes ahead of time. Whenever you move a light or a static mesh near one, the bake goes out of date. In UE5, Lumen lights everything in real time, so many projects don’t need baking at all.
| Your project | Best fix |
|---|---|
| Lumen, real-time lighting | Turn static lighting off (Step 2) |
| Baked lighting for performance (mobile, VR, low-end PCs) | Build the lighting (Step 1) |
| Mixed, or you’re not sure | Make the lights Movable (Step 3) |
Step 1: Build the lighting
- Open the Build menu in the main toolbar.
- Choose Build Lighting Only.
- Wait for the bottom right progress to finish, then save the level.
For a quick test, set Build > Lighting Quality to Preview. Use Production for the final bake.
Step 2: Turn static lighting off (Lumen projects)
- Open Edit > Project Settings > Rendering.
- Search for Allow Static Lighting and untick it.
- Restart the editor when asked.
Lumen and real-time shadows then handle everything, and the message stops for good.
Turning off Allow Static Lighting removes all baked lighting from the project. Only do it if you aren’t relying on lightmaps for performance.
Step 3: Make the lights Movable
Select each light, and in the Details panel set Mobility to Movable. Movable lights never need building. Check Sky Light and Directional Light too: they’re the usual culprits.
Step 4: Turn baking off for one level
Open Window > World Settings, expand Lightmass, and tick Force No Precomputed Lighting. Then run Build Lighting Only once to clear the old data.
FAQ
The message is back after I moved something. That’s normal with baked lighting. Build again after you’ve finished placing things.
Can I hide the message without fixing it? The console command DisableAllScreenMessages hides on-screen messages, but the lighting is still unbuilt.
Lighting build takes forever. Use Preview quality while working, and lower the lightmap resolution on large meshes.