Fix activity files without handing them to anyone.
Repair a recording your watch did not finish saving, join a ride that got split in two, or convert between FIT and GPX. The work is done by your browser, on your device. The files are never uploaded.
- Repair a FIT fileRecover a recording that was cut off or will not upload. Rebuilds the missing summary and checksum..fit
- Join activitiesTurn a ride or run that was split into several recordings back into one activity..fit .gpx
- FIT to GPXGet a GPX track, with heart rate, cadence and power, out of a device recording..fit → .gpx
- GPX to FITTurn a recorded GPX track into a FIT activity file..gpx → .fit
How it works
When you choose a file, the page reads it directly from your disk, processes it in this tab, and gives you the result as a download. There is no server step, so there is no upload limit, no queue and no account. You can load a tool page, switch off your connection, and it will still work.
An activity file holds where you were, second by second, usually starting and ending at your front door. That is a good reason not to send it to a website you found five minutes ago, and it is the reason this one is built the way it is.
What it will not do
- Recover data that was never written. If the device lost power at kilometre 30, the repaired file ends at kilometre 30.
- Blend two recordings of the same activity, such as heart rate from a watch into a ride from a bike computer. Joining is for recordings made one after another.
- Upload anything to Garmin Connect or Strava for you. You get a file; you choose where it goes.
How the output is checked
The code is tested against real recordings from Garmin watches and bike computers. Files the tools write are read back by a separate, independently written FIT decoder running in strict mode, which rejects a file with a wrong checksum or an incomplete record. That shows the files are structurally valid FIT. It does not guarantee how any particular platform will treat them, so look over the summary the tool shows you before you upload.