Publishers produce fashion magazines. Retailers sell fashions. Those boundaries will blur on Friday with the launch of Porter, a glossy new fashion magazine created by online luxury retailer Net-A-Porter.

The publication that hits newsstands Friday won't look much different from other high-fashion titles. Porter doesn't splash shopping information across its fashion spreads. There's a famous model on the cover—Giselle Bündchen—a chatty feature on actress Uma Thurman, and 282 pages of articles and photo spreads, as well as...