As long as you are using a flat-bottom wok or a round bottom wok with a wok ring, glass-top stoves are safe to use. The only exception to this rule is hand-hammered woks. These are covered in small divots leftover from the manufacturing process. While useful for cooking, these divots can concentrate the weight of your wok and potentially scratch or crack your stovetop. Instead, opt for stamped or spun woks, which offer many of the same benefits.