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 the usual answer has been a form on someone's website where you type in record numbers.
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; on the sample ride, cutting thirty minutes took it from 39 km and 2:23 to 34 km and 1:54 with the map redrawn. 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, which is the part other tools get wrong.
Fix a field over a selection
Heart rate, power, speed, cadence, elevation and temperature. 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.
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. It refuses files that overlap in time rather than guessing.
Repair
A file that won't upload after a crash can often be partially decoded; the editor keeps what it can read and tells you the rest was unreadable.
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 an honest comparison page that points you at GOTOES when you need GPX or TCX.
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
