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Merge FIT files

Merge several FIT files into one FIT activity, in time order. Use it when a bike computer or watch split a ride into pieces after a crash or a battery stop. Heart rate and times stay, and nothing is uploaded.

How to merge FIT files

  1. 1Drop all your .fit files in at once
  2. 2Check the notes about gaps and overlaps
  3. 3Click "Save FIT" to get one merged file
  4. One FIT file with every part, in time order.

What happens to your files

  • Nothing is uploaded.Your FIT files are read and joined by your browser, on your own device.
  • A real FIT file comes out.The saved file has a header and checksum, so Strava and Garmin Connect can read it.
  • Heart rate and times stay.Every point keeps its time, position, elevation and sensor values.

What you can do

  • Join several FIT files into one, sorted by when each one starts.
  • Keep a gap between two files as a pause instead of counting it as moving time.
  • Fill sensor values that one overlapping file lacks, such as heart rate, from the other one.
  • Mix in GPX or TCX files if a part exists only in that format.
  • Save as FIT, or as GPX or TCX if the next app prefers that.

Good to know

  • The saved FIT file holds the record data: time, position, altitude, heart rate, cadence, power and temperature. Laps, devices and other messages from the originals are not copied.
  • FIT needs a time on every point. If a file has none, "Save FIT" stays off and the page tells you to use "Fix times" or save as GPX.
  • A damaged FIT file is read as far as it goes, and a warning names it.

Questions

How do I combine two FIT files?

Drop both files on this page, check the notes, and click "Save FIT". The result is one activity in time order.

Will Strava or Garmin Connect accept the merged file?

The file is written as a standard FIT activity with a header and checksum, which is what those services expect.

Does merging keep heart rate and power?

Yes. Heart rate, cadence, power and temperature stay on their points.

Are my FIT files uploaded?

No. They are merged in your browser and never leave your device.

Related tools

How it works

Small tools that run in your browser.

Four steps

  1. Start with a file or a task

    Drop a file, search, or pick a task.

  2. The tool opens in a window

    Open as many as you like, side by side as tabs.

  3. Results collect on the right

    Drag a result into the next tool.

  4. Save when you're done

    Saved files go to your downloads.

Who uses what

Tool sets for common jobs.

Put a tool on your home screen

The icon opens that tool, like an app.

iPhone and iPad

  1. Open the tool in Safari.
  2. Tap Share (the square with the arrow).
  3. Choose “Add to Home Screen”, then Add.

Android

  1. Open the tool in Chrome.
  2. Tap the menu (⋮) at the top right.
  3. Choose “Add to Home screen” or “Install app”.

Computer

  1. Open the tool in Chrome or Edge.
  2. Click the install icon in the address bar.
  3. Choose Install.

Skills

Claude skills we use ourselves, one job each.