How to Use the Light Level Overlay to Find Dark Spots

The light overlay paints a number or color on each block showing its light level. This is the fastest way to find spots where hostile mobs can spawn, or to confirm a room is fully lit.

Enabling and choosing a mode

In the config screen, enable the light overlay. Most versions let you switch between a numeric display (the actual light value on each block) and a colored mode where blocks are tinted by how dark they are. Numeric mode is more precise; colored mode is easier to scan across a large area at a glance.

Hunting spawnable spots

Walk through the area you care about and look for blocks showing low light. Hostile mobs need darkness to spawn, so any block below the safe threshold is a candidate. Check floors, corners, under overhangs, and the tops of walls where light does not reach. Fix each dark block by adding a light source nearby, then re-scan to confirm the number rose above the threshold.

Verifying a finished build

After lighting a room, sweep the whole floor and walls with the overlay on. If every block reads above the safe level, the room is spawn-proof for hostile mobs. Use the same check on mob farm spawning platforms to confirm they are dark enough for mobs to actually spawn where you want them.