WHEN Tim Zagat dines out in New York, many of the restaurants he goes to know that he prefers his soup served in a cup and enjoys iced tea with cranberry juice in a large glass over lots of ice. Jay-Z’s fondness for white Burgundy is also no secret among the city’s headwaiters.

But what is perhaps more surprising is that when Arnie Tannen, a health care consultant in Brooklyn, sits down for his regular Friday-night dinner at Gramercy Tavern, his server always knows that he prefers a black napkin (less lint) and wants only the ends of a loaf in his breadbasket.

Those details are carefully logged in the restaurant’s computer, and Mr. Tannen suspects that the tavern has also noted his love of French fries, even though it does not serve them. For his 68th birthday in 2011, his waiter surprised him with hot fries hurried in from a nearby spot.

“You never have to say anything more than once,” Mr. Tannen said of the service.

Part of the attention paid to his preferences can be chalked up to the owner, Danny Meyer, and his well-known obsession with highly personalized hospitality. But what most customers don’t know is that hundreds of restaurants are now carefully tracking their individual tastes, tics, habits and even foibles.