The Split edits GPS/heart-rate activity files (FIT, TCX, GPX) with no install and no account. Upload one or two files, pick an operation, preview the result, and export. Files are processed in memory and automatically discarded after a short time — see Privacy for details.
Drop your primary file on the home page. Depending on what it contains and whether you add a second file, the tool shows only the operations that make sense for that pair — a single-session run only offers Merge, Crop/Split, or Concatenate; a multisport file also offers boundary editing and, if a matching secondary overlaps one of its legs, Substitute leg.
Combine two recordings of the same session into one file, aligned by timestamp with a manual or auto-detected clock offset. Which data is imported depends on the pair, and the tool decides that for you: with a heart-rate source (typically a TCX export from a chest or arm strap) it replaces the activity's heart rate, keeping the original wherever the second file has no reading or one below a sane 40 bpm; with two recordings of one ride — a watch or bike computer plus a virtual platform such as Zwift, MyWhoosh or TrainingPeaks Virtual — it brings the platform's route, distance, speed and altitude into your own device's recording, which keeps the device identity Garmin Connect credits the ride to.
Trim an activity to a time or distance range, or split one recording into two separate activities at a chosen point — useful for removing a warm-up, cutting off a forgotten trailing recording, or separating two races captured in one file.
Join two activities that were recorded back-to-back (for example after a dropped GPS lock caused an auto-pause) into a single continuous file, with the second one's timing rebased to start right after the first.
Move the transition point between sessions in a multisport file (swim → bike → run) by dragging it on the chart, or enter official race transition times in bulk. Lap and session stats on both sides of the boundary are recalculated, and a lap straddling the new boundary is split rather than misassigned.
If one leg of a multisport recording is missing or corrupted but you have a separate single-sport recording that overlaps it, splice that recording's data into the matching session.
Download the result in the same format your primary file was in — FIT stays FIT, TCX stays TCX, GPX stays GPX. Concatenate is the one exception: since it joins two files, it lets you pick which of the two source formats the combined file exports as.
Garmin and other Garmin-SDK-compatible FIT files, Polar and other TCX exports, and GPX tracks. Exports come back in the same format you uploaded (Concatenate lets you choose between its two source formats instead), as long as that format can represent the data you have — GPX, for example, has no field for heart rate or laps, so it's unavailable as an export when the result depends on either.
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