UL stands for Underwriters' Laboratories, an American organisation that tests whether electrical products are safe — plugs, chargers, extension cords, kettles, and so on. It also tests things like fire doors and drinking water equipment, and it writes safety standards that manufacturers follow. When a product passes, it may carry the UL mark, a small circle with the letters UL inside, usually stamped on the plug or moulded into the plastic. American buyers look for that mark the way people in Taiwan look for the BSMI 商檢局 mark. Two honest cautions. UL is a private company, not a government body — it earns money from the testing it does, so its mark means "tested to a standard", not "approved by the US government". And the mark is one of the most faked marks in the world; cheap chargers online often carry a UL logo that was never earned. Say the letters one at a time: U-L.