Multi-stream compare

All parsing and comparison happens in your browser — your .fit and .gpx files never leave your device. Drop up to three files (e.g. power meter + smart trainer + HRM), then switch between Power / HR / Speed / Cadence to see how the devices compare on each metric. The first file becomes the time-axis reference; the others are DTW-aligned to it.

Sensor library: 0 saved

Preferences: metric · light · 8 decimals

PDF report— cover + KPI table + chart + segments

Aero lab— estimate CdA from power + speed + altitude

Bias lab— linear bias + dynamic response + Mahalanobis outliers

Brand— defaults (JoyAnalyze)

Custom metrics— 0 saved · 0 active on chart

Open API— 0 tokens · 0 webhooks

Radar taillight specialist— upload a FIT or paste JSON of radar events

Upload FIT

Upload a .fit recorded with a Garmin Varia or Wahoo ACE taillight, or paste a JSON array. The panel will compute detection-distance, alert, accuracy, and response-latency stats.

Shootout templates

— pre-fill labels and metric

Streams (3 / 20)

Drop A.fit / .gpx here

or click to browse

Drop B.fit / .gpx here

or click to browse

Drop C.fit / .gpx here

or click to browse

Drop up to three .fit or .gpx files above

We will parse the streams, align them with DTW against the first file, and overlay the chosen metric on the same time axis. Try a "shootout" template below for sensor comparison.

How to use

Ride once with 1-3 devices recording simultaneously — e.g. a power meter (Quarq / Favero / 4iiii), a smart trainer (Tacx / Wahoo / Zwift Hub), and a heart rate monitor (Wahoo / Polar / Garmin) on the same ride.
Export each recording as .fit or .gpx and drop them into the slots above. The first file you drop becomes the time-axis reference.
Switch between Power / HR / Speed / Cadence to see how the devices compare on each metric. The chart applies a per-stream DTW alignment so the curves line up correctly even if one device dropped samples or paused.

What we measure

For each non-reference stream, JoyAnalyze reports a DTW total cost (lower = better agreement), mean time offset, and max time offset. The summary cards show distance, duration, average and max HR, and average / max / normalized power for every loaded file.

See the JoyAnalyze roadmap →