The three formats at a glance
In short: GPX is the universal, track-focused format, TCX adds training structure (laps, heart rate, cadence), and FIT is the compact, complete native format of GPS watches and bike computers. Let's look at each in detail.
GPX — the universal one
GPX (GPS Exchange Format) is an XML text file, born to exchange tracks between devices and mapping software. It's the most universally accepted format: nearly every sport, hiking and mapping app reads it. It stores a sequence of GPS points (latitude, longitude, elevation, timestamp). Heart rate, cadence or temperature only appear through optional extensions that not every app can read.
Best for: sharing a route, importing a course into a GPS, exchanging a track between apps. Its limit: it isn't really a training-analysis format.
TCX — structured training
TCX (Training Center XML), created by Garmin, is also a text file, but organised around the sport activity rather than just the track. It structures data by lap and natively includes distance, time, speed, heart rate and cadence. It's heavier than GPX for equivalent content, but better suited to analysis. Some coaching platforms or older software only work with TCX.
Best for: keeping training data (heart rate, laps) when the target won't accept FIT. Its limit: less universal than GPX, more verbose.
FIT — the watch format
FIT (Flexible and Interoperable data Transfer) is Garmin's native binary format, adopted by Wahoo, Coros, Suunto, Bryton and most modern devices. Being binary (not text), it's very compact yet stores a huge amount of data: GPS, heart rate, cadence, power, temperature, running dynamics, sensor data. It's the richest of the three, but also the only one unreadable without a dedicated tool — double-clicking shows only binary.
Best for: keeping an activity's full data, archiving, detailed analysis. Its limit: less universally accepted than GPX, and impossible to open by hand.
So which should you choose?
It all comes down to what the destination accepts and what you want to keep:
- You're just sharing a route (hike, bike course) → GPX, readable everywhere.
- You're importing into a platform that wants heart rate/laps but rejects FIT → TCX.
- You're archiving or analysing an activity without losing anything → FIT, the most complete.
- You don't know what the target accepts → try GPX first (most compatible), then TCX if heart rate is lost.
Moving from one format to another
Good news: you're not stuck with the original format. You can convert from one format to another while keeping all compatible data, right in your browser — no upload, no sign-up.
Useful reminder: conversion reorganises existing data, it doesn't invent any. Converting a GPX with no heart rate into TCX won't make heart rate appear. To keep everything, start from FIT when you can.
See what a file contains
Not sure what's in your file? The viewer opens any GPX, TCX or FIT and shows the track, elevation and available data — handy to check before converting or importing.