What is a FIT file?
FIT (Flexible and Interoperable Data Transfer) is the binary file format used by Garmin and other fitness devices to store activity data. It contains GPS coordinates, heart rate, cadence, power, temperature, and hundreds of other data fields recorded during your workout.
While Garmin Connect provides basic analysis, this tool gives you deeper insights — including per-lap breakdowns, HR zone distribution, pace charts, and the ability to export raw data to CSV for custom analysis.
How FIT Analyzer Works
FIT Analyzer parses the binary FIT protocol directly in your browser using JavaScript — no server upload required. The FIT (Flexible and Interoperable Data Transfer) format stores data in a series of messages: file header, definition messages that describe the data structure, and data messages containing the actual values. The analyzer decodes device info, session summaries, lap splits, record-level data (every 1–5 seconds), and event markers. It then presents this in a readable dashboard with summary statistics, split tables, and time-series charts. Unlike platform-specific tools, FIT Analyzer shows you everything the device recorded, including developer fields and undocumented metrics.
Common Issues When Analyzing FIT Files
Multi-sport FIT files (triathlon, duathlon) contain multiple sessions in a single file. Some tools only show the first activity — FIT Analyzer processes all sessions and labels them by sport type. If your file shows zero heart rate data, check whether the HR sensor was paired during the activity; some chest straps disconnect briefly and create gaps. GPS-only activities (no HR strap, no power meter) will naturally show fewer metrics — the analyzer adapts its display based on available data fields. Corrupted FIT files from interrupted syncs or low battery shutdowns may fail to parse; try re-syncing the activity from your device to Garmin Connect and re-exporting.
How to export your FIT files
In Garmin Connect, open any activity, click the gear icon, and select "Export Original." This downloads the .fit file. You can also find FIT files on your device — connect via USB and look in the Garmin/Activity folder.