Files: GPX, FIT and TCX 3 MIN READ
.fit.gz files: what they are and how to open them
A .fit.gz is an ordinary FIT file compressed with gzip. Strava's bulk export is full of them. How to open one, when you need to unzip it first, and how to convert it to GPX in the browser.
A `.fit.gz` file is a FIT file in a gzip wrapper. The FIT inside is exactly what the watch wrote — what a FIT file is — and the `.gz` is the same compression as a `.zip`, applied to one file at a time. It exists to make downloads smaller, and you meet it in one place above all: Strava's bulk export.
Why Strava's export is full of them
Request your archive — the bulk export guide — and the `activities` folder holds one file per activity, in whatever format Strava received it. Activities from a Garmin, Wahoo or Coros are FIT, and Strava compresses each to `.fit.gz`. Activities recorded with the Strava app are GPX and are not compressed. The `activities.csv` next to them lists which is which.
Opening one without unzipping
You usually do not need to unzip. The FIT file viewer reads `.fit.gz` as it is and draws the route with distance, time and elevation; the editor takes them straight into a print; the heatmap generator takes a whole folder of them at once. All in the browser, nothing uploaded.
When you do need the plain .fit
Some tools want an uncompressed file. Strava's own help notes that a FIT downloaded from Garmin Connect comes zipped and must be unzipped before uploading it to Strava — the same applies to a `.fit.gz` going back the other way. To unzip:
- Mac: double-click the file. The `.fit` appears beside it.
- Windows: right-click, *Extract*, or use 7-Zip. Windows does not open `.gz` on its own in every version.
- Command line: `gunzip file.fit.gz`.
Converting to GPX
If the tool you are going to needs a GPX, FIT to GPX reads the `.gz` directly and writes a GPX with position, elevation and time. Heart rate and power stay behind, because GPX has no standard place for them; if they matter, keep the `.fit` and use a tool that reads it.
If it will not open
A `.fit.gz` that unzips to nothing, or to a file every tool refuses, is a damaged archive entry, not a damaged recording — the original is still on Strava as an activity, and *Export Original* on the activity page gives it to you again. If the FIT itself is damaged, repair a FIT file.
Questions people actually ask
- What is a .fit.gz file?
- A FIT file — the watch's recording — compressed with gzip. Unzipped it is a normal .fit; the .gz just makes it half the size for the download.
- How do I open a .fit.gz file?
- Drop it into the FIT file viewer or the editor here; both unzip it on the fly. To get the plain .fit out, unzip it: double-click on a Mac, or use 7-Zip or the built-in extractor on Windows.
- How do I convert .fit.gz to GPX?
- Drop it into the FIT to GPX converter — it reads the .gz directly and gives you a GPX with position, elevation and time. Several at once is fine.
- Why are the files in my Strava export .fit.gz?
- Because a Strava export is every activity you ever uploaded, and most of them arrived as FIT from a device. Compressing them makes the archive a fraction of the size. Strava keeps the original file it received; the .gz is only the wrapping.
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