What is FIT File Editor?
Strava lets you trim the start and end of an activity and that is it. Forgot to stop the watch at the cafe, had the heart rate strap read 220 for ten minutes, recorded a ride on the wrong bike profile, or split one run across two files when the watch died: none of those are fixable on Strava, and fixing them used to mean a different single-purpose tool for each problem.
FIT File Editor puts the whole activity on one timeline instead. The map sits on top, every data stream sits below it as a lane, and you drag across a range to select it. A popover offers Cut, Edit or Zoom. Cut removes the range, including from the middle, and the laps and totals recompute. Edit lets you cap, set, smooth, fill or clear a field across just that range. There is undo and redo, ⌘Z works, and nothing leaves the browser.
It does not connect to Strava. You export the original file from an activity's three-dot menu, fix it here, delete the original on Strava and upload the new one. The site says Strava and Garmin Connect accept the result because the totals are recalculated and the file is valid, and it warns that a few Garmin badges also check the unit's serial number, which the editor leaves as recorded.
Key Features
Cut anything
Drag across a section and cut it. A cut in the middle inserts paired timer stop and start events and the session and lap totals are recomputed.
Fix a field over a selection
Heart rate, power, speed, cadence and elevation. Cap a spike, set a flat value, smooth it, fill a gap by interpolating, or clear it. The change applies only to the range you selected. You can also type the real total distance in the details panel, and distance, speed and pace scale to match across the whole activity, for a treadmill run, an indoor ride or a wrong wheel size.
Adjust GPS
Drag a point to move it, right-click to delete one, or smooth a selected stretch or the whole track. Useful for the tunnel that sent you across a river.
Change what the file says about itself
Sport and sub-sport from a list, the device manufacturer (Garmin, Wahoo, COROS, Suunto, Polar, Hammerhead, Zwift and others) and product ID, the activity name, and the start date and time. A time shift moves records, laps, sessions and the summary together.
Merge
Two or more files back to back, with distance carrying across the join.
Combine two devices
For two recordings of the same session, say a watch with heart rate and a bike computer with power, open the one you want to keep and add the other. Heart rate, power, cadence, GPS, elevation, temperature or speed that the first file is missing is filled in from the second, matched by time and only where the two overlap. Nothing the first file already recorded is changed, so if both have heart rate, the first file's stays. The editor decides on its own: files that overlap in time are combined, and files that don't are joined end to end.
GPX and TCX
A GPX or TCX activity opens in the same editor and exports as FIT, with heart rate, cadence and power kept when the file carries them. It comes in as one lap, with no device until you pick one. Any activity can also be saved as GPX, which keeps the track and the common sensor data but drops laps and the device.
Repair
For a watch that died mid-activity or a sync that got cut off, the repair keeps every record it can read, drops the broken part and writes a valid file with the totals recalculated, then tells you what was unreadable. Data the device never wrote can't come back, and some older devices use a compressed timestamp format it can't read yet.
Built for developers too
The site publishes a vendor-neutral FIT format reference under a Creative Commons licence, with a plain-Markdown copy for AI agents, and a comparison page of six FIT file tools that points you at GOTOES for joining many files or starting from CSV.
Who It's For
- Anyone who forgot to stop the watch and wants the cafe stop gone from the middle, not just the end
- Riders with a spiking heart rate strap or a power meter dropout who want the stretch fixed, not the whole ride deleted
- People who recorded on the wrong profile and want the sport or device corrected before Strava sees it
- Runners whose watch died mid-race and have two files that should be one
Does FIT File Editor connect to Strava?
No. Export the original file from the activity's three-dot menu on Strava, edit it, then delete the original and upload the new file. The editor works on files only; it doesn't connect to Strava or Garmin.
What formats does it open?
FIT, GPX and TCX, and a Garmin Connect Export Original zip opens as it is. It exports FIT, or GPX if you want the track. A planned route or course with no timestamps won't convert, some older recordings with compressed timestamps can't be read yet, and settings and sleep files aren't activities, so they won't upload anywhere.
Is my file uploaded anywhere?
No. Decoding, editing and re-encoding run in a worker inside your browser, and the site says the file is never uploaded to a server. The site keeps its own log of events, such as a file being opened or exported, with no IP addresses and no cookies, and also uses Google Analytics, which sets its own cookies, but the file stays on your machine.
Will Strava or Garmin Connect accept the edited file?
The site says yes, because the totals are recalculated and the file is valid, and it tells you to delete the original upload first so it does not appear twice. Changing the device can affect Garmin badges that check the serial number, which the editor does not change.
Who makes FIT File Editor?
The home page says it was built by an ultrarunner and triathlete who kept needing to fix their own files.
Can it edit laps or split a file?
Not yet. Laps recompute when you cut, but there is no lap editor, no split, and no per-record table.
