AI Serve Coach for Tennis
Get instant feedback on your serve technique after every rep — using only the Apple Watch already on your wrist. No camera. No coach. No guessing.
Free · Requires iPhone & Apple Watch (watchOS 11+)
Get instant feedback on your serve technique after every rep — using only the Apple Watch already on your wrist. No camera. No coach. No guessing.
Free · Requires iPhone & Apple Watch (watchOS 11+)
Most recreational tennis players never get consistent feedback on their serve mechanics. Lessons are infrequent. Video review takes time. Self-assessment is unreliable.
Swingli's AI Serve Coach solves this by using the motion sensor in your Apple Watch to analyze the biomechanics of each serve automatically. Every time you serve in practice mode, the watch captures a dense stream of motion data — gyroscope and accelerometer readings at up to 100 samples per second. That data is analyzed against the motion patterns of a technically sound serve, and the result appears on your iPhone within seconds.
You get feedback on four specific technique elements after every single serve, every time you practice.
The position at the peak of your toss — racket dropped behind the back, elbow elevated, body coiled. This loads your shoulder and core for the forward swing. Without it, serves become arm-only and lose both power and consistency.
The backswing arc that takes the racket from the trophy pose into the slot position before swinging forward. A full, relaxed loop stores elastic energy in your shoulder and elbow. Rushed serves skip the loop and lose racket head speed.
Where the racket meets the ball — ideally at full arm extension, slightly in front of the body, reaching up and forward. The AI coach evaluates the deceleration signature at the peak of your swing to assess contact height and direction.
The inward forearm rotation that fires at and just after contact — the "snap" responsible for most of the speed on flat serves and spin on kick serves. Many recreational players finish palm-up instead of rotating through. The gyroscope detects this directly.
After each serve, your iPhone shows a results screen with a card for each of the four elements. Each card is rated Good or Needs Work based on the motion data from that serve.
Below the four cards, the AI coach identifies your single highest-priority focus area — the one element most likely to improve your serve if you work on it — with a short explanation and a link to a tutorial video showing the correct technique.
This keeps practice structured. Rather than trying to fix everything at once, you have one clear target per session.
At the end of a serve practice session, Swingli shows your pass rate for each technique element across all serves. This makes it easy to spot whether a weakness is consistent (appears on most serves) or situational (appears only when you're going for pace or serving to a specific zone).
There's no minimum session length. A 5-serve warmup check works just as well as a focused 30-serve practice block.
The AI Serve Coach also works during full game sessions. After you finish a game, Swingli analyzes all detected serves from your session and generates a technique summary. This is separate from the per-serve practice feedback — it gives you a higher-level view of how your serve held up over an entire match or hit session.
The game-mode analysis typically appears within a minute of ending your session, as a banner at the top of your session summary screen.
Apple Watch uses a three-axis gyroscope and three-axis accelerometer that together capture rotational velocity, linear acceleration, and directional movement in six dimensions. During a tennis serve, this sensor array records the full arc of the motion — from the toss arm lift through the trophy pose, the loop, the forward swing, contact, and follow-through.
Swingli's detection algorithm runs on the watch itself and identifies serve motions in real time. The motion path data is then sent to the analysis engine, which evaluates it against biomechanical benchmarks for each of the four technique elements.
No video processing. No special equipment. The sensor that makes this possible is already on your wrist.
Download Swingli free and run your first serve practice session. You'll see exactly which technique elements to work on before you leave the court.
Free · Requires iPhone & Apple Watch (watchOS 11+)
Swingli's AI Serve Coach checks four technique elements on every serve: trophy pose, loop, contact point, and wrist pronation. Each is evaluated independently from your Apple Watch motion data and rated Good or Needs Work.
No. The AI Serve Coach uses only the motion sensors in your Apple Watch — gyroscope and accelerometer. No camera, no video, no extra equipment.
Within a few seconds of completing each serve. Analysis is automatic — serve, then glance at your iPhone before the next rep.
Yes. The AI Serve Coach is included in the free Swingli app on the App Store.
Any Apple Watch running watchOS 11 or later — Series 4 and newer, SE (2nd generation), and all Ultra models. iPhone requires iOS 18 or later.
Yes. After any game session, Swingli analyzes all your serves and shows a technique summary with pass rates across all four elements. This complements the per-serve feedback you get in dedicated serve practice mode.
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