At a corridor or event entrance, you may need to know how often people pass in each direction. Tallying every crossing by hand can be difficult.
Browser Kitty's Passage Counter counts people crossing a line on a camera view or local video, keeping A→B and B→A events separate.
These are crossing events, not unique visitors. A person who walks out and returns counts twice.
Detection and counting run locally without uploading footage. Results can be inaccurate, so check a short session first.
1. Choose a camera or recorded video
Open Passage Counter. Select Start camera for a live view or Local video for a recording stored on your device.
Mount the camera so the passage is visible and keep it stationary. Grant camera access in your browser.
The browser must support decoding the selected video. Being able to choose a file does not guarantee playback.
2. Position the counting line across the passage
Position the displayed line over the passage. Drag its middle to move the entire line; drag either white endpoint to change its length or angle.
Place it where people will cross and reverse A/B if the directions are opposite to what you need.
The line is locked during the setup check and active counting, so set it before starting.
3. Run the 30-second camera check
In camera mode, select Start 30-second check to verify detection and direction. Trial events are excluded from your measurement.
Moving the line requires another check. Walking through the monitored area can help reveal a misplaced or reversed line.
Local-video mode does not require the 30-second check.
4. Start counting by direction
Select Start counting to record A→B and B→A crossing events. Video analysis starts from the beginning and ends at the end of the clip.
A person who crosses A→B and later returns B→A adds one event in each direction. The app does not deduplicate people.
Keep the page visible while measuring a live camera. Backgrounding the tab can interrupt counting.
5. Correct missed or extra crossings
Occlusion, obstacles and lighting may cause the automatic count to be wrong.
Use +1/−1 on either direction tile to correct the total. Undo beside the total reverses the latest manual correction.
Automatic crossings, manual corrections and undo actions are distinguished in the history and Events CSV.
6. Finish and export CSV
Pause and resume if needed, then finish. Periods not observed due to camera interruption are marked as missing, not zero crossings.
Events CSV contains crossings, corrections and undo; Summary CSV contains directional totals and duration; Time buckets CSV contains 5/15/60-minute counts and observed time.
Check the filename and save. CSV uses UTF-8 with BOM and does not include the original video or audio.
7. Review saved sessions
Session records are stored in the same browser and can be reopened under Saved sessions.
The original video and persistent person IDs are not saved. Reopening the page does not automatically restart the camera or reload the video.
Session records are not shared across browsers, devices or sites. Export important results to CSV.
Accuracy and browser limitations
Overlap, backlighting, darkness, fast crossings or camera movement may cause missed or incorrect counts. Accuracy is not guaranteed.
The browser must support WebAssembly SIMD and decompression. Sustained Android/iPhone testing and accuracy validation on 100+ real crossing events remain incomplete.
For safety, billing or legal uses, independently verify the results rather than relying on them alone.
Are videos and counts uploaded?
Person detection and crossing counts run inside your browser. Camera frames and selected video are not uploaded to a counting server.
MediaPipe, EfficientDet-Lite0 and WASM are embedded in the HTML. The hosted page downloads initially, but it does not send video to a remote AI API.
A supported browser can run the standalone HTML offline. Camera access from file:// may be restricted depending on the browser.
Passage Counter
Count A→B and B→A line-crossing events in a fixed camera view or local video.
References
See the Passage Counter README for usage and limitations, and its future-work document for pending accuracy and device validation.
- Passage Counter Usage and limitations (README)
- Passage Counter Pending field and physical-device testing