Backyard Lap Timer
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Choose who is driving, which car, and where you are racing.
Drivers
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Tap a driver to use them in your next session.
Add driver
Cars
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Choose a car or review its setup.
Add car
Tracks
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Choose the track for your next session.
Add track
Sharing & access
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Invite one of your drivers to a track. Track invitations appear in Community.
Sign in to manage track sharing.
Results
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Browse sessions saved on this device or compare cloud track records in Leaderboard.
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One best lap per track. Conditions and car describe the winning session. Race totals are grouped only by lap target and require every lap to be valid.
Track records
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Cloud records across devices and members of your shared tracks. One best lap per track; best race totals are grouped by lap target. Car and conditions describe the winning result, not separate rankings. Full session details stay on the recording device.
Sign in to view cloud track records.
Race
Next session
Change the driver or car, then start another session. Your camera and track setup stay ready.
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Open the camera, draw the finish line, and calibrate before starting.
1 Camera & finish line
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This slider uses camera-controlled zoom when supported. Otherwise it enlarges the image digitally; digital zoom adds no detail. Changing zoom clears the finish line, so draw it again.
Open the camera to enable zoom.
Finish line settings
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Zone size controls the area watched around the line. Count direction refers to movement in the camera image, regardless of how you drew the line. These adjustments are remembered for the selected track on this device.
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Calibration sets this threshold for the current lighting. Raise it to ignore small movements; lower it if car passes are missed. Recalibrate when lighting or camera position changes.
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Crossings sooner than this minimum are detected but ignored by the lap timer to prevent duplicate laps. Choose a value below the fastest possible lap on this track.
Draw a line, then calibrate with the track empty.
2 Detection
Open the camera and draw a finish line to begin.
3 Session Setup
Target: 10 laps
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Recorded with the session and its record. Conditions and cars do not create separate track lap records.
Choose a track to set the session condition.
Ghost reference
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References show best lap and valid laps total. Same track, layout, surface, condition and direction. Invalid laps make a session ineligible as a Ghost reference. Gap and voice update at each completed lap; negative means ahead.
Session: Idle
Live timing
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Projection uses completed-lap average after 2 laps, excluding pauses. Ghost gap updates at the line.
Waiting for detection to start.
Lap history
| Lap | Time | Delta to best |
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Session summary
Community
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Add drivers, accept track invitations, and compare best times.
Sign in to manage drivers and shared tracks.
Your drivers
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Add a driver using their unique Backyard nickname.
Invitations
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Driver requests and invitations to race on a shared track.
Settings
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Open a group to manage your account or adjust this device.
Account & profile
Sign in or create an account
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Keep using the timer without an account. When you sign in, this device’s guest drivers, cars, tracks, and saved sessions are automatically merged into your account. Your original guest copy stays on this device.
Checking sign-in availability…
Profile photo
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Uses your account photo, including the Google photo when provided. Upload a personal photo to replace it. Your photo is visible on drivers linked to your account.
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Your nickname is a unique @name other drivers use to find you (3–24 letters, numbers, underscores or hyphens). Your public name is shown on leaderboards.
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The app automatically backs up driver, car and track profiles, car setup notes, and best-result summaries. It never uploads individual laps, complete session files, camera settings, or video. First sign-in automatically merges this device’s guest history into its account copy.
Import a backup file
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Use this only to bring in an exported JSON backup from another browser or device. Guest data on this device is merged automatically at sign-in.
No backup selected.
Delete cloud data
This removes your cloud profile and shared records. Your local copy remains on this device.
Two-device setup (optional)
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Connect two devices on the same Wi-Fi: choose Sensor on the camera phone and Viewer / Controller on the other device. Both devices need internet briefly to find each other. Sign in to the same account on both and make each device available for five minutes. On the Viewer, select the Sensor; approve the request on the Sensor. The Viewer shows the camera and session controls. The Sensor handles timing and saves results. Connect them before mounting the Sensor phone.
Connect devices with your account
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This device stays hidden until you make it available. Sign in to the same account and make both devices available. Choose the Sensor from the Viewer, then approve the request on the Sensor. Keep both devices on the same Wi-Fi.
Sign in to the same account on both devices, then make each device available.
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Keep both devices on the same Wi-Fi. If they cannot connect, check that neither is using a guest Wi-Fi network and turn off any VPN. The Viewer shows the Sensor camera and controls; timing and saved results stay on the Sensor.
Single-device mode.
Phone & detection test
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Open the camera, draw the finish line, and start detection on Race. Return here while detection is running, then make a pass across the line. This panel records the analyzer frame at the center-line timestamp used for timing and reports this phone’s observed processing rate.
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Precision estimate is one analysis-frame interval at the measured FPS. Camera exposure, motion blur, lighting, and thresholding can add error; this is not a laboratory accuracy measurement.
Zone motion: A — · center — · B —
Camera setting: — FPS · requested: 60 FPS
Screen Wake Lock is inactive.
Frame used to mark the passage time
No passage captured yet. Start detection and make a car pass the finish line.
Last candidate: —
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This experimental detector estimates a crossing from motion through zones A, center and B. It does not identify a specific car; people, shadows, camera shake and other movement may trigger it. Processing and captured frames stay on this device.
Sound alerts
Install the app
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Add Backyard Lap Timer to your home screen for quick access. Open this page in the browser listed below first.
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- Open this page in Safari.
- Tap Share (the square with an up arrow).
- Tap Add to Home Screen (you may need to scroll).
- Tap Add to confirm.
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- Open this page in Chrome.
- Tap the three-dot menu ⋮.
- Tap Install app or Add to Home screen.
- Confirm Install or Add.
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- Click the install icon in the address bar, if shown.
- Choose Install.
- Alternatively, open the browser menu and select Install Backyard Lap Timer.
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If an install option does not appear, use the latest version of a supported browser and check its menu. Installing adds an app shortcut; your sessions remain stored on this device.
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Race remembers zone size, direction, motion threshold, and minimum lap for each track on this device. Camera, sound, and session preferences also stay on this device. Clearing site data removes these preferences.
Viewer / Controller
Waiting for Sensor…
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Drag on the camera preview to set the finish line. The Sensor applies the line and all controls.
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Controls zoom on the Sensor. It uses camera-controlled zoom when available, or digital zoom through this same slider otherwise. Redraw the finish line after zooming.
Finish line settings
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Zone size is the area watched around the Sensor finish line. Count direction is movement in its camera image. These settings are remembered for the selected track on the Sensor device.
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Raise the threshold to ignore small movements, or lower it if passes are missed. Calibrate again when lighting or camera position changes.
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Passes earlier than this minimum are ignored by the lap timer. Set it below the fastest possible lap on the track.
Save this session?
Only saved sessions count toward records. Discarding will not update history or cloud records.
Consistency: —