The 18-year-old American entered eight events, giving her a chance to match Michael Phelps as the only swimmers to win that many events at a major championship.
But, after a tough double on Tuesday and a lackluster showing in the morning preliminaries, Franklin and her coach, Todd Schmitz, decided to scratch the 50 backstroke a non-Olympic event that she swims mainly for fun, though she did take bronze at the 2011 worlds in Shanghai.
There was only a 20-minute break between the semifinals of the 50 back and the final of the 200 free, and the latter was much more important to Franklin. She just missed a medal in that event at the London Olympics, losing out for third by a hundredth of a second.
"We decided that maybe the risk kind of outdid the rewards," Franklin said. "So we decided not to do it. It was fun to swim it this morning but I'm really happy with the decision to scratch and just do this."
France's Camille Muffat went out hard, leading after the first lap and 0.75 under the world-record pace. But Franklin edged ahead at the midway point and held off hard-charging Federica Pelligrini of the Italy, the world-record holder, to win in 1 minute, 54.81 seconds.
Pelligrini claimed silver, 0.33 behind the winner, while Muffat settled for the bronze.
Midway through the swimming portion of the championships, Franklin still has four events to go. She'll be a big favorite in the 200 back, and she'll be on two more relay teams that have a good shot at gold. The 100 free presents her biggest challenge, though it would be foolish to put anything past Franklin.
She was fifth in that event at the Olympics, but has spent the past year working diligently to improve her freestyle stroke.
That was obvious in the 200 free.
"We're coming down the mountain now," Franklin said. "This is what we prepared for, this kind of event through eight days. I'm really, really happy with my swim there. You kind of use each swim to motivate you for the next swim."