diff --git a/src/main/java/dan200/computercraft/client/render/DebugOverlay.java b/src/main/java/dan200/computercraft/client/render/DebugOverlay.java
new file mode 100644
index 000000000..9545ab7c5
--- /dev/null
+++ b/src/main/java/dan200/computercraft/client/render/DebugOverlay.java
@@ -0,0 +1,61 @@
+/*
+ * This file is part of ComputerCraft - http://www.computercraft.info
+ * Copyright Daniel Ratcliffe, 2011-2021. Do not distribute without permission.
+ * Send enquiries to dratcliffe@gmail.com
+ */
+package dan200.computercraft.client.render;
+
+import dan200.computercraft.ComputerCraft;
+import dan200.computercraft.api.turtle.ITurtleUpgrade;
+import dan200.computercraft.api.turtle.TurtleSide;
+import dan200.computercraft.shared.peripheral.monitor.TileMonitor;
+import dan200.computercraft.shared.turtle.blocks.TileTurtle;
+import net.minecraft.client.Minecraft;
+import net.minecraft.tileentity.TileEntity;
+import net.minecraft.util.math.BlockRayTraceResult;
+import net.minecraft.util.math.RayTraceResult;
+import net.minecraftforge.api.distmarker.Dist;
+import net.minecraftforge.client.event.RenderGameOverlayEvent;
+import net.minecraftforge.eventbus.api.SubscribeEvent;
+import net.minecraftforge.fml.common.Mod;
+
+import java.util.List;
+
+@Mod.EventBusSubscriber( modid = ComputerCraft.MOD_ID, value = Dist.CLIENT )
+public class DebugOverlay
+{
+    @SubscribeEvent
+    public static void onRenderText( RenderGameOverlayEvent.Text event )
+    {
+        Minecraft minecraft = Minecraft.getInstance();
+        if( !minecraft.options.renderDebug || minecraft.level == null ) return;
+        if( minecraft.hitResult == null || minecraft.hitResult.getType() != RayTraceResult.Type.BLOCK ) return;
+
+        TileEntity tile = minecraft.level.getBlockEntity( ((BlockRayTraceResult) minecraft.hitResult).getBlockPos() );
+
+        if( tile instanceof TileMonitor )
+        {
+            TileMonitor monitor = (TileMonitor) tile;
+            event.getRight().add( "" );
+            event.getRight().add(
+                String.format( "Targeted monitor: (%d, %d), %d x %d", monitor.getXIndex(), monitor.getYIndex(), monitor.getWidth(), monitor.getHeight() )
+            );
+        }
+        else if( tile instanceof TileTurtle )
+        {
+            TileTurtle turtle = (TileTurtle) tile;
+
+            event.getRight().add( "" );
+            event.getRight().add( "Targeted turtle:" );
+            event.getRight().add( String.format( "Id: %d", turtle.getComputerID() ) );
+            addTurtleUpgrade( event.getRight(), turtle, TurtleSide.LEFT );
+            addTurtleUpgrade( event.getRight(), turtle, TurtleSide.RIGHT );
+        }
+    }
+
+    private static void addTurtleUpgrade( List<String> out, TileTurtle turtle, TurtleSide side )
+    {
+        ITurtleUpgrade upgrade = turtle.getUpgrade( side );
+        if( upgrade != null ) out.add( String.format( "Upgrade[%s]: %s", side, upgrade.getUpgradeID() ) );
+    }
+}