Lighting in Scenes is not Consistent between builds and editor/playmode.

I started building out my game scene, it was always well lit when I hit the play mode button to test it out.

Normal Lighting

Then created a new scene for my Main Menu. I added some buttons, when you click one the scene switches to my game scene, it’s clear something is wrong!

Poorly Lit

Hunting the internet I found a result on Unity Answers. Bullet points are added by me for clarity.

Explanation from Zitoox:

  • When you select a scene, Unity will automatically bake all the lights and render things.
  • BUT when you open a scene while playing the game in the editor, Unity will NOT bake the lights,render them, fix the effects and all, and this causes everything to stay dark.
  • This only happens in the editor. If you build your game, you will see that this will not happen.

And a fix from Arwym:

  • go to Window -> Lighting. In that Window, look for the “Debug Settings”.
  • Untick the “Auto Generate” checkbox and hit the “Generate Lighting” button beside it.

In my version of Unity I needed to go via Window > Rendering > Lighting:

Getting to Lighting

And then click the Generate button:

Generate