Device rebooted mid-ride and left you two halves? Drop them all here — formats can be mixed — and get back one continuous activity, sorted by time, distance recomputed across the seam.
Every trackpoint from every file is pooled and sorted by timestamp, so the order you upload in doesn’t matter. Cumulative distance is recomputed across the whole merged track — the second file’s odometer no longer resets to zero at the seam. Heart rate, cadence, power and temperature ride along.
Yes — merge a FIT with a GPX with a TCX. Each file is parsed to a common representation first. Output as a FIT activity (best for Strava / Garmin Connect), GPX, TCX or CSV.
Device crashed and restarted mid-ride; watch battery swapped at an aid station; commute recorded in segments; two people’s recordings of the same tour stitched for one map.
Your file is never written to disk. It is parsed in memory, converted, sent back, and garbage-collected. No accounts, no tracking pixels, no “files are deleted after 24 hours” fine print — there is nothing to delete.