The Internet allows sellers to track “window shoppers,” consumers who look but do not buy, and to lure them back later by targeting them with an advertised sale. This new technology thus facilitates intertemporal price discrimination, but simultaneously makes it too easy for a seller to...

I derive a social planner's optimal information design in an environment with quasi-hyperbolic discounting consumers without commitment. Consumption induces instantaneous utility, but unknown delayed cost. Consumers may or may not acquire additional costless information on the cost parameter....