Can I fix just one part of the activity?

Yes. Drag across the section you want and the change applies there only. The rest of the activity is untouched.

How do I get rid of a heart rate spike?

Select the spot, pick heart rate, and cap it to a sensible maximum, or smooth it. The average updates to match.

Can I fix the elevation or the GPS track?

Yes. You can smooth or correct elevation over a selection, and in Adjust GPS mode you can drag a point back onto the road, smooth a stretch, or delete a stray fix.

Can I correct the total distance?

Yes. Open the details panel next to the file name and type the real total. Distance, speed, and pace scale across the whole activity, which fixes a treadmill run, an indoor ride, or a wrong wheel size.

My file won't open or upload at all. Can this fix it?

That's a repair rather than a data fix. Open the file anyway: the editor recovers every record it can read, drops the damaged part, and exports a clean file. The repair page walks through it.

Will the totals stay right?

Yes. FIT File Editor recalculates averages and maxes from the edited data, and the export is a valid .fit file.

Fix the data in a FIT file

Select any part of the activity and fix the numbers there. Cap a heart rate spike, smooth a power dropout, redraw a stretch of GPS, or correct the elevation, then export a clean file. The rest of the activity is left alone.

Open the editor Compare the tools Free, and nothing leaves your browser.

A heart rate trace with a spike from a dry strap. Drag across the spike, then press Smooth.

Bad data never survives contact with a drag.

The FIT File Editor with a section selected and the edit panel open to cap a heart rate spike — Select a section, pick the data to change, and choose how to fix it. The change applies to that range only.

What you can fix

A heart rate spike from a dry strap or a loose chest belt.
A power dropout, or a meter that read high after a bad calibration.
Elevation that's off because the barometer drifted.
A cadence or speed sensor that cut out for a stretch.
A GPS track that wandered off the road, or a single stray point.

How it works

Open your file and drag across the part you want to fix on the timeline.
Pick the data to change: heart rate, power, speed, cadence, or elevation.
Choose how: cap a ceiling, smooth it, set a value, fill a gap, or clear it.
For the GPS track, turn on Adjust GPS to drag, smooth, or delete a point.
Export the corrected file and upload it.

Questions

Can I fix just one part of the activity?: Yes. Drag across the section you want and the change applies there only. The rest of the activity is untouched.
How do I get rid of a heart rate spike?: Select the spot, pick heart rate, and cap it to a sensible maximum, or smooth it. The average updates to match.
Can I fix the elevation or the GPS track?: Yes. You can smooth or correct elevation over a selection, and in Adjust GPS mode you can drag a point back onto the road, smooth a stretch, or delete a stray fix.
Can I correct the total distance?: Yes. Open the details panel next to the file name and type the real total. Distance, speed, and pace scale across the whole activity, which fixes a treadmill run, an indoor ride, or a wrong wheel size.
My file won't open or upload at all. Can this fix it?: That's a repair rather than a data fix. Open the file anyway: the editor recovers every record it can read, drops the damaged part, and exports a clean file. The repair page walks through it.
Will the totals stay right?: Yes. FIT File Editor recalculates averages and maxes from the edited data, and the export is a valid .fit file.