Convert FIT, GPX, and TCX files in your browser.

Drop the FIT file into the converter, pick GPX as the target format, and download. The conversion runs entirely in your browser. Routes, elevation, timestamps, heart rate, and cadence carry through. Power gets written into the Garmin TrackPoint extension. The whole process takes about a second and the file never leaves your device.

Drop the GPX into the converter and pick FIT as the target. The output is an activity-typed FIT with each GPX trackpoint as a record message, timestamps preserved, and elevation carried through. If you want a navigable course FIT (with turn prompts) instead of an activity FIT, use our [GPX to FIT Course Converter](/tools/gpx-to-fit-course) - that tool detects turns and writes course_point waypoints.

No. The converter uses the official Garmin JavaScript FIT SDK and the browser's native XML parser, both of which run entirely in your browser. The bytes never leave your machine, nothing is logged, no analytics ping carries any file content. The only network call the page makes is to load the page itself; after that, you can disconnect the wifi and the converter still works.

FIT is Garmin's binary activity format - small files, rich metadata, holds power and laps and device info, but you cannot open it in a text editor. GPX is the universal XML route format - readable in any text editor, holds trackpoints and elevation, but lacks first-class slots for power and lap structure. TCX is Garmin's older XML format - heavier than GPX but with native HR/cadence/power and lap data. Use FIT for full fidelity, GPX to share with anyone, TCX for legacy platforms that demand it.

GPX has no first-class slot for power or lap structure. The converter writes power into the Garmin TrackPoint extension (which most platforms read), and HR/cadence into the standard GPX extensions. Lap boundaries are written as waypoints. Device info, session totals, and FIT-specific event messages do not have GPX equivalents and are dropped. If you need full preservation, keep the FIT or convert to TCX instead.

For analysis outside the standard training platforms. JSON gives you the entire decoded FIT as a nested object - every message, every field, every record - which is the format you want for custom scripts or for diffing two files. CSV exports just the per-second record stream (time, lat, lon, elevation, HR, power, cadence, speed) which is what spreadsheets and Python pandas want. Use JSON for full structure, CSV for time-series work.

Yes - the output is a fully valid FIT re-encoded via the official Garmin SDK with correct CRC and headers. Strava treats it like any other upload. If the original file was already in Strava and you are re-uploading the converted version, you will hit duplicate detection - either delete the original first or shift the start time using our [FIT Time Adjuster](/tools/fit-time-adjuster).

One file at a time today. If you need to merge two or more files into a single activity, use our [FIT Combiner](/tools/fit-combiner). For true batch workflows (a folder of files all converted), drop a note via the waitlist and we will prioritise.