Convert FIT (device activity file) to GPX

A FIT file is a compact binary export straight off a GPS watch or bike computer, and while it holds the richest possible record of a ride or run, that richness is also what makes it awkward to share: most consumer tools, route-planning sites, and even some coaching platforms simply expect GPX instead. This converter walks every record message in the FIT stream — position, elevation, timestamp, heart rate, cadence, power, temperature — and re-encodes it as GPX trackpoints, because GPX's job is portability rather than completeness. That tradeoff shows up in three places worth knowing about before you convert: power survives only through a vendor extension GPX was never designed to carry, distance and speed are dropped entirely since GPX has no element for either, and lap boundaries disappear because GPX has no lap concept at all — a recording gap becomes a second track segment instead. Position, elevation, timestamps, heart rate, and cadence carry over cleanly. None of this happens on a server: the FIT bytes are parsed and rewritten entirely inside your browser tab, in a background worker thread, so a three-hour ride with a quarter million trackpoints doesn't freeze the page while it processes, and the file itself never leaves your device. If your goal is simply to get a route into the widest possible range of downstream tools without a login or an upload dialog, GPX is the safest landing format FitFileHub writes, and this page does exactly that conversion, free, for files up to 25 MB.