Thwack Golf

Turn your iPhone into an offline launch monitor. Set it on a tripod, hit a shot, and see ball speed, launch angle, direction, estimated carry and a tracer video.

Thwack turns the iPhone you already own into a launch monitor and shot tracer for the range. Put your phone on a tripod, address the ball, swing, and Thwack shows your numbers a few seconds later. No sensors on the club, no extra hardware, and no account.

HOW IT WORKS

1. Mount and aim. Set your phone on a steady tripod behind or beside the ball. Thwack uses the motion sensors to check that the phone is still and level.
2. Lock the ball. Address a white or yellow ball. Thwack finds it, locks focus and exposure, and arms for impact.
3. Swing. Thwack films around impact with the high-frame-rate camera and tracks the ball through the first frames of flight.

WHAT YOU SEE AFTER EVERY SHOT

• Ball speed (mph or km/h)
• Launch angle
• Start direction left or right of your target
• Estimated carry, calculated with a ball-flight model
• Estimated backspin and sidespin, based on typical values for the club you picked (un fortunately not measured, I couldn't figure out how to do it. if you have any ideas, leave a 4 star review with your suggestion!)
• A shot tracer video you can save to Photos or share

Numbers that aren't measured directly from the ball's flight are clearly labeled as estimated.

BUILT FOR PRACTICE

• Sessions and history: every shot is saved on your phone with its numbers and clip, so you can look back later.
• Course mode: play fictional practice layouts hole by hole using your own shots.
• Big-screen numbers: AirPlay or use an HDMI adapter to show ball speed, launch and carry on a TV.
• Your choice of tracer color, plus imperial or metric units.

PRIVATE BY DESIGN Everything runs on your iPhone. Thwack works in airplane mode, doesn't need an account, and never uploads your video or shot data. Your shots stay on your phone until you delete them.

WHAT YOU NEED

• An iPhone running iOS 17 or later with a high-frame-rate (slow-motion) camera
• A tripod or other steady mount
• A white or yellow ball that stands out against the background
• Daylight or a well-lit hitting bay

Thwack is a practice tool, not a scientific launch monitor. Results depend on lighting, camera placement and how clearly the ball can be seen, so please use the numbers to spot trends and compare shots.