Merge activities into one file

A watch that dies partway through a long ride and gets restarted a few minutes later leaves you with two files instead of one — the same problem shows up when a recording was paused and resumed, or a route was tracked in separate segments across different devices. Uploading either piece alone gives you an incomplete activity; uploading both as separate activities splits stats that should really be one continuous effort. What you actually want is a single file that picks up where the first one left off. The tricky part is rarely just concatenating files — it's handling the overlap. If a device was restarted quickly, or two people recorded the same stretch on separate devices, the files often share a window of time where both have points. Guessing which points to keep in that overlap can silently duplicate or drop data. FitFileHub's merge tool detects time-overlap between the files you're combining and lets you choose how to resolve it directly, rather than making that decision for you: keep one file's points for the overlapping window, or interleave points from both. Files are ordered by their actual recorded start time, not by upload order, so it doesn't matter which order you drop them in — a file recorded second slots in after the one recorded first automatically. It also works across mixed formats, so a GPX segment and a FIT segment from a watch swap mid-activity can be merged into one output file without a separate conversion step first. The result is a single continuous activity with correctly ordered, non-duplicated timestamps throughout. As with every FitFileHub tool, merging runs entirely in your browser — none of the segments are uploaded anywhere to be combined. Free for files up to 25 MB per file, three files per batch.