Two phones. Both players. One match.
We're building a tennis tracker that films a match from both ends: every shot up close, 3D ball tracking, line calls on both sides, and a coach that watches both players. To work on your court, it has to see many courts. Send us a match and get a free year of Pro when we launch.
Works with one phone. Two phones make it better. Founding spots: 100 solo · 50 duo.
First to 5 against the tracker · mouse, finger or ← →
You won 5–3
- Shots
- 0
- Fastest
- 0km/h
- Winners
- 0
- Errors
- 0
- Longest rally
- 0
- Best today
- 0
The app does this for real matches, for both players, from two phones on the fence.
Hit the ball near the edge of your racket for sharper angles. Too sharp goes out.
Forty seconds. Sound on.
The far side is where tracking breaks.
Mount one phone behind your baseline and your opponent's half shrinks to a strip at the top of the picture. A ball out there is only a few pixels wide, and a player's body hides it at the moment of the hit.
is how wide a ball at the far baseline appears in a 1080p video from one phone. When we tested our own single-phone tracking on matches it had never seen, most missed shots came from the far side.
A second phone behind the other baseline films every shot up close. Hits, bounces and line calls come from whichever phone is nearer, and technique analysis finally works for the player at the far end too.
The same moment from both phones, enlarged 11 times. Each square is one pixel of a 1080p video.
Tracking, stats and a coach for both of you.
One phone tracks your match. Two see every shot up close.
On your own, one phone behind your baseline tracks the whole match. Add your partner's phone behind the other baseline and both line up automatically: hits, bounces and in/out calls come from the nearer camera, the ball is tracked in 3D, and highlights cut between both angles.
One session, two players
You and your partner share one match. Each of you gets serve speeds, depth, errors, win rates by shot and a personal highlight reel.
A coach that watches both ends
Close-up video of each player makes technique analysis work from both ends: contact point, swing path, footwork. The coach connects it to your points, shows you the clips, and builds a weekly plan with drills the app measures.
Built for club tennis in Europe: clay, indoor halls and floodlights. The analysis runs on your phone. Solo works everywhere; duo is the upgrade.
Your match, filmed like this.
- Where
- Behind the baseline, centered, on the fence
- Height
- 2–3 m, higher is better
- View
- Landscape, whole court in view: both baselines, all four corners
- Video
- 1080p or 4K at 60 fps (30 fps works too)
- Length
- 20 min or more of real play, no cuts, no zoom
- Sound
- On: the sound of the racket helps us find the hits
- People
- Everyone recognizable is 18 or older and agrees
- Duo
- Optional: a second phone behind the other baseline, same match
From your court to the model.
Record
Film a match or point play with the setup above.
Upload
Send the video and answer a few questions: surface, city, phone, mount height.
Automatic check
We check court view, frame rate and length. You hear back within a few days.
Your Pro year
Accepted matches get a free year of Pro at launch and a beta invite, while spots last. Duo matches earn one for each player.
We train on the ball, not on you.
One purpose
Your video is used to train and test ball and shot tracking. Nothing else.
Never public
We never publish or sell it, and never use it in ads without asking you first.
Stored in the EU
For training we keep cut-outs around the ball. Faces are not what the model learns from.
Gone on request
Write to burolab.office@gmail.com and we delete your video and everything made from it within 30 days. Models already trained can't un-learn it; later versions won't use it.
Ready when your match is.
Before you upload, have these at hand. The upload form asks for them.
- Court surface and indoor or outdoor
- City and country
- Phone model and roughly how high it was mounted
- Singles or doubles
- Both videos of the same match, named phone A and phone B
- Your email, so we can send your Pro code
Before you ask.
Why not just use an existing tracking app?
Existing apps film from one end, so the far side stays small and blurry. We're building for two phones, stats for both players and a coach on top of that. If you already film with a tracking app, your raw recordings without overlays are exactly what we need.
Do I need two phones?
No. The app works with one phone, and solo matches are just as welcome. Duo matches have their own spots and earn a Pro year for each of the two players.
Which phones work?
Any recent iPhone or Android phone that records 1080p at 60 fps. A fence mount or clamp keeps it steady.
Can I send practice sessions?
Yes, as long as there are real rallies and serves. Point play is best.
Can juniors take part?
Not for now. Everyone recognizable in the video has to be 18 or older.
When does the app launch?
Everyone with an accepted match gets invited to the beta first, and the free Pro year starts at launch.
Terms and privacy.
The full texts sit with all buroLAB legal pages: submission terms, privacy notice and legal notice. In short:
Submission terms, in short
- Adults only. Everyone recognizable in the video is 18 or older and has agreed.
- You recorded the video or have the right to share it, and you pass our privacy notice on to the other players.
- You give buroLAB · Daniel Buro a non-exclusive, free, worldwide right to store, copy and analyze the video and data derived from it (such as ball positions and cut-outs) to develop, train and test Ballmark's tracking and coaching software. The right ends when you withdraw. We never publish or sell your video, and use it in marketing only with your separate permission.
- Each accepted submission earns one year of Pro from launch while spots last: 100 solo, 50 duo (one code for each of the two players). One code per person, no cash. Accepted means it passes the automatic technical check. We plan to launch but cannot guarantee it.
- You can withdraw at any time by email. We delete the video and derived data within 30 days; models already trained keep what they learned. Your Pro code stays valid.
- German law applies; mandatory consumer protection in your country of residence stays unaffected.
Privacy, in short
- Controller: buroLAB · Daniel Buro (sole proprietorship), Habelstr. 1, 65719 Hofheim am Taunus, Germany, burolab.office@gmail.com.
- This page is hosted by Cloudflare, Inc., USA (EU-U.S. Data Privacy Framework), which processes IP addresses to deliver and protect it (Art. 6(1)(f) GDPR). No cookies, no tracking, nothing stored on your device, nothing loaded from other servers. The game runs only in your browser.
- Your video and form answers are processed with your consent (Art. 6(1)(a) GDPR) to train and test ball and shot tracking; your email to send your Pro code (Art. 6(1)(b)). Other players agree themselves. People on camera by chance are covered by our legitimate interest (Art. 6(1)(f)) and cropped out; you can object.
- Videos are stored in the EU with a provider bound by a data processing agreement; training runs on our own computers in Germany. No face recognition, nothing public. We keep the data while we need it for development, and no longer than until you withdraw.
- You have the right to access, correction, deletion, restriction, portability and objection, can withdraw consent at any time, and may complain to a supervisory authority.