Two Different Brewing Methods
Cold brew is steeped in cool water for around 20 hours. No heat is involved at any point. Iced coffee is brewed hot at double strength and then chilled, so it goes through the same process as a hot cup before being cooled down.
That single difference produces every other difference between them. Heat pulls acids and aromatic compounds out of coffee quickly. A long cold steep pulls out far fewer of them, which is why cold brew reads rounder and sweeter with no sugar added.
Taste and Body
Iced coffee keeps the bright, sharp notes of a hot brew and reads thinner in the mouth. It takes milk and syrup well, which is why the standard Starbucks iced coffee arrives sweetened by default unless you say otherwise.
Cold brew is smoother, heavier in body and noticeably less acidic. It stands up on its own without sweetener, which is the main reason people who drink coffee black tend to prefer it.
Caffeine and Calories
Cold brew carries more caffeine per ounce. The long steep extracts a large amount and the drink is served without dilution beyond ice. Nitro cold brew runs higher still, since it is served without ice at all.
On calories the two start in the same place, which is nearly zero. What separates them in practice is the default build. Standard iced coffee comes sweetened, and cold brew comes plain, so the drink as ordered usually differs even though the base does not.
Which to Order
For caffeine, cold brew. For a lighter, brighter cup that takes milk and syrup well, iced coffee. For the smoothest black coffee on the cold menu, nitro cold brew, which adds a thick head and a soft texture from the nitrogen.
Every one of these has its own page here with the published panel per size, including the caffeine figure. Browse them under coffee and espresso.
