How to edit a FIT file on a Mac
Search for a FIT file editor and the first results are Windows programs. The Fit File Repair Tool needs Windows and Microsoft Access components, and several of the smaller utilities are .exe downloads. On a Mac, the practical choice is an editor that runs in the browser.
The short answer
FIT File Editor runs in Safari, Chrome, Firefox, or Arc on macOS. There is nothing to install and no account. The file is decoded, edited, and written back on your Mac. It never goes to a server, which matters if the activity is private or the file is large.
It handles the jobs people usually need:
- Crop a section out, including from the middle, which Strava can't do.
- Fix a heart rate spike, a power dropout, a wandering GPS point, or bad elevation.
- Merge two recordings after a watch died partway.
- Change the device, sport, or start time, and rename the activity.
- Repair a file that won't upload.
Getting the file onto the Mac
From a Garmin or Wahoo over USB. Plug it in. Garmin devices show up as a drive in Finder, with the activities in Garmin/Activity. Newer Garmin watches that use MTP don't mount in Finder; use Android File Transfer or, more simply, export from Garmin Connect instead.
From Garmin Connect. Open the activity, click the gear icon, choose Export Original, and unzip the download.
From Strava. Open the activity, click the three-dot menu, choose Export Original.
From an Apple Watch. Apple doesn't write FIT. Apps like HealthFit export your workouts as FIT files to iCloud Drive, where the Mac can see them.
Editing
- Open the site and drag the file onto the page, or press browse and pick it in Finder.
- Make the edit. The activity is on one timeline under the map, and the stats update as you go.
- Press Export. The file goes to your Downloads folder with the same name.
- Delete the original activity on Strava or Garmin Connect, then upload the edited one.
If you'd rather have a desktop app
GoldenCheetah is free, open source, and runs natively on macOS. Editing is a side feature there, done in a spreadsheet-style view, and it can rescue some broken files. It's a good choice if you already use it for analysis. For the full list, including the Windows-only tools, see the comparison.