Exposed Copper Bulb is one of four oxidation stages of the copper bulb family, added to Java Edition in 1.21 and Bedrock Edition in 1.21.0. Exposed Copper Bulb emits light level 12 while lit, one step down from an unoxidized copper bulb's level 15, because copper bulbs dim from 15 to 12, 8, and 4 as they oxidize further. Exposed Copper Bulb toggles instantly between lit and unlit whenever it receives a redstone pulse, then keeps that state afterward without any continuous power. A comparator reads Exposed Copper Bulb's state and outputs signal strength 15 when lit or 0 when unlit, regardless of oxidation stage, so a comparator and copper bulb pair can act as a compact T flip-flop.

Crafting Exposed Copper Bulb takes three Exposed Copper Blocks, one Blaze Rod, and one Redstone Dust arranged on the crafting grid, yielding four bulbs per craft. Lit, waxed copper bulbs also generate naturally inside trial chambers in random oxidation stages. Scraping Exposed Copper Bulb with an axe removes its oxidation, while waxing it with a Honeycomb stops further oxidation entirely. An observer even detects the red dot that flashes on Exposed Copper Bulb whenever it gets powered or unpowered. Redstone builders use Exposed Copper Bulb for compact toggle lamps and comparator-driven flip-flop circuits that need a slightly dimmer light than a fresh, unoxidized copper bulb, without wiring up a full clock.