Zpeed Blog

Building a GPS Speedometer PWA

How a browser can become a lightweight GPS speedometer with PWA support.

Published January 10, 2025. Updated May 22, 2026.

A GPS speedometer PWA combines the browser Geolocation API, a readable speed interface, installable web app metadata, and careful permission timing. The page should be useful before it asks for location, then request GPS access only when the user starts tracking.

The important performance decision is to keep the runtime small. Zpeed should load the speedometer shell immediately and only run the code needed for live speed tracking, unit conversion, trip distance, elapsed time, and GPS accuracy display.

GPS speed is not always available directly from the browser. A practical speedometer needs a fallback path that calculates movement between location samples, rejects noisy jumps, and avoids counting tiny GPS drift as real travel distance.

A service worker can improve repeat visits, but it must be versioned carefully so users receive updates after each deployment. HTML and the service worker should revalidate quickly, while stable icons, fonts, and scripts can be cached longer.

The best PWA experience is quiet: a fast first load, a clear Start button, saved unit preferences, and an install prompt only when the browser supports it.