Three taps between you and a better swing.

The camera records at 240 frames per second. That matters more than it sounds. A driver takes roughly a quarter of a second to travel from the top of the backswing to the ball, so at the 30 fps most phones default to, the entire downswing is seven or eight frames — and impact itself almost never lands on one of them. At 240 fps you get eight times the detail, and the frame you actually care about exists.

Framing is the one thing SwingOK cannot fix for you. Down-the-line, the phone sits behind you on the target line; face-on, it sits square to your chest. Get the whole club and both feet in shot, keep the camera still, and shoot somewhere with enough light that the shutter stays fast — a blurred clubhead is a blurred clubhead no matter how good the model is.

The strike is the loudest, sharpest transient in the recording, and it is far easier to find in the audio track than in the pixels. SwingOK listens for it, marks that instant as the anchor frame, and trims the clip around it. That's why there's no timer to beat and no partner holding the phone — you swing, and the clip that comes back already starts at address and ends at the finish.

From there, pose estimation runs over the trimmed clip on the phone's own neural engine, placing 33 body landmarks — shoulders, elbows, wrists, hips, knees, ankles, heels, toes and the points on your face used to fix head position — on every single frame. Those landmarks are what every angle downstream is derived from: shoulder turn, hip turn, the separation between them, spine tilt, and where your hands are relative to the ball.

The landmark track is sampled at the checkpoints coaches already use: P1 through P10, from address to the finish, with impact as P7. Each checkpoint has a small number of things worth measuring at that moment — face-on hip depth at P4, shaft position at P5, hand height at P6, shaft lean at P7 — and each is compared against the range that's typical for a swing that works.

Then comes the part most swing apps get wrong. You will usually be out of range on several checkpoints at once, because swing faults cascade: one early move creates three late compensations. Reporting all of them is how you end up with a dashboard you scroll past. SwingOK returns the single change furthest upstream — the one whose fix collapses the others — plus the drill that trains it. Then you film again and watch the number move.