Plain-language policy

Private by construction.

Effective 27 August 2026. Stroke Lab runs in your browser. We do not receive your strokes or diagnostic reports.

What the lab processes

The lab temporarily processes pointer timestamps and coordinates so it can draw raw and smoothed traces. Aggregate timing—including sample rate, gaps, frame delay, and undo duration—stays in the current browser tab.

What exports contain

JSON exports contain timing aggregates, diagnostic findings, capability flags, and notes you enter. Stroke coordinates are excluded by default. Pressure and tilt are excluded by default and are only recorded for future strokes after you select the corresponding control. The bundle is downloaded directly by your browser.

Storage and network use

We use no accounts, cookies, analytics, advertising, tracking pixels, cloud stroke storage, or third-party scripts. A service worker may cache public site files on your device so the lab remains available offline. You can remove that cache through your browser’s site-data controls.

Your control

Use “Clear test” to remove the current tab’s measurements, close the tab to discard the session, and delete any exported bundle through your device’s file manager. Review a bundle before attaching it to an issue.

Contact

For privacy questions, open an issue in the Stroke Lab repository. Do not include sensitive drawing content in a public issue.