What it can't do yet

It sees from one side only

One camera can't measure movement towards or away from it. A head moving sideways, or a shot filmed from behind the baseline, isn't measured properly.

Film side-on, as the filming guide shows.

It doesn't measure racket speed, spin or where the ball goes

The Swing Score rates your movement: head stability, balance, and how low you load and hold it. A club player with sound fundamentals can score close to a pro, so use it to improve, not to rank players.

Serves get three measures, not the full set

Serve reports cover leg drive, contact height and shoulder tilt. Footwork and balance measures are built for groundstrokes and aren't used on serves.

It follows one player

If other people are in the shot, it locks onto one player and notes when someone else appears. Check that the skeleton in your video stays on the right person.

Timing is best with sound

The moment of contact is timed from the sound of the hit. Without sound, it falls back to the video frames, which is less precise.

A player it can't track is turned away

If the player is too far away or can't be found, the upload check stops it rather than guess. Dark, grainy or heavily compressed footage gets a warning, because it can throw the scores off.

Most of our test footage is of teenage and adult players

Scores take your height into account, so a smaller player isn't judged on an adult's distances. We're still checking junior footage, and under-10 red and orange ball tennis (lower bounce, smaller court) hasn't been checked yet.

It isn't medical advice

"Looking after your body" points out positions that put extra load on a joint. It isn't a diagnosis. If something hurts, see a physio or doctor.

Numbers move a little between sessions

Tracking wobbles slightly, so each score shows its margin: the Swing Score is good to about 3 points either way. To compare sessions, film the same way each time.