How to use the online timer
Twelve minutes suits a standard drop cookie of average thickness in a moderate oven, though softer, chewier styles want less time and thin, crisp ones can want more — the dough itself matters as much as the number on the timer. Chilling the dough beforehand, even for twenty minutes, keeps cookies from spreading into thin, greasy discs and gives a thicker, more even result.
Cookies are notorious for looking underdone right when they need to come out. The edges should be set and lightly golden while the centre still looks slightly soft and underbaked — that centre firms up entirely during the few minutes it sits on the hot tray after coming out of the oven, which is exactly why a cookie that looks perfectly done inside the oven is usually already overdone once it cools.
Rotating the tray halfway through the bake evens out oven hot spots, which matter more in cookies than almost any other bake because of how thin and quick they are. Let them sit on the tray for a couple of minutes before moving them to a rack — try to lift a fresh-from-the-oven cookie too soon and it'll likely fall apart in your hand.
Common questions
Why do my cookies look underdone when I take them out?
That's expected — the centre should look slightly soft in the oven since it firms up as the cookie cools on the tray. Pulling them once they look fully set inside the oven usually means overbaked.
How do I stop my cookies spreading too thin?
Chill the dough for at least twenty minutes before baking. Warm dough spreads much faster in the oven than chilled dough does.