BikeSync combines Garmin heart rate and physiology with Zwift power, cadence, GPS route, distance, and elevation into one upload-ready FIT file for Garmin Connect, Strava, and TrainingPeaks — entirely in your browser. No uploads, no account, free.
The default Garmin + Zwift preset uses Garmin as the master timeline for heart rate, temperature, Body Battery, Stamina, laps, and calories, while Zwift fills power, cadence, route, GPS, distance, speed, altitude, and elevation. BikeSync recomputes ride summaries and preserves useful FIT messages where possible.
Record the session on both devices as usual, then export both FIT files — Zwift saves activities as .fit, and Garmin Connect offers “Export Original” on the activity page. Drop the Garmin file into slot A and the Zwift file into slot B, merge, and download one combined ride.
Recording one indoor session on both a Garmin and Zwift produces two overlapping activities — one with your best heart-rate and physiology data, one with power and the virtual route. Merging combines them into a single complete file, so you upload one activity instead of choosing which half of your data to keep.
Yes — that is the default preset. The merged file keeps Garmin heart rate, temperature, Body Battery, Stamina, laps, calories, and device identity, and takes power, cadence, speed, distance, elevation, and the virtual route from Zwift.
Auto-align cross-correlates signals recorded by both devices — cadence, heart rate, or power — to find the exact offset. If the files share no signal, BikeSync falls back to each file’s clock time, and you can always set the offset manually and merge again.
The preset is tuned for Garmin + Zwift, but BikeSync accepts any two FIT activity files of the same ride — for example a bike computer plus another indoor training app. File A always wins for heart rate and physiology; file B fills power, cadence, and route.
No. FIT decoding, alignment, merging, recomputing, and encoding run locally in your browser. Your Garmin and Zwift files are never sent anywhere.
Yes. No account, no subscription, and no file uploads — the entire merge runs in your browser. Donations are welcome but never required.