What Strava says
Strava’s help explains that “Improperly formatted data” means the file is incompatible with Strava: its data is corrupted, missing information or improperly formatted. Strava accepts .fit, .gpx and .tcx files, and these formats are strict.
Strava adds that such files often come from Garmin devices that had a recording error, or from tools that create or convert GPX files. Its own advice is a reset of the device or contacting the manufacturer. That helps the next activities, not the file you already have.
Users also report the message “The upload appears to be malformed and we are unable to process it” when uploading a .fit file. The cause is the same: Strava cannot read the file to the end.
Other Strava errors that look alike
“Empty” file: according to Strava, a .fit file that is empty is usually corrupt and often extremely small (sometimes 72 bytes); such files cannot be repaired. FIT Rescue says so too when a file has no readable activity data.
“Corrupted time data”: the date jumps into the future in part of the file. FIT Rescue removes points with impossible or backwards times, but if the clock was wrong for the whole activity, the real date cannot be guessed.
“Time information is missing”: the file has positions without times, often a GPX drawn by hand. It is not a damaged .fit file, and there is no time to recover.
Repair the file, step by step
Take the .fit file
The original file of the activity, from the GARMIN/Activity folder of the watch or from the original export in Garmin Connect.
Open it in FIT Rescue
The diagnosis shows what makes the file unreadable: a cut-off end, a wrong size or checksum, damaged bytes, a missing summary.
Apply the repairs
Check the before and after, then download the repaired .fit file.
Upload it to Strava again
Use Strava’s file upload with the repaired file.
What FIT Rescue repairs
- A file cut in the middle of a message, or with damaged bytes in the middle
- A wrong data size, a wrong or missing checksum
- A missing session or activity summary after a crash
- Points with impossible or backwards times, GPS jumps, heart rate and power spikes
What it cannot do
- An “empty” file with no readable activity data
- A clock that was wrong for the whole activity
- A GPX without times, or a file that is not a FIT file at all
- The part of the activity that was never written to the file
Repair the refused file
Drop the .fit file that Strava refuses: you see what is wrong and download a repaired file.
Questions
What does “The upload appears to be malformed” mean on Strava?
Strava could not read the file to the end. With a Garmin .fit file, the recording usually stopped abnormally (battery, freeze, crash while saving) and the file was never closed properly.
Will Strava accept the repaired file?
I cannot guarantee it: Strava decides. The repaired file follows the FIT protocol, its size and checksum are right and it is read back without error before you download it.
Should I upload a GPX instead?
Strava accepts GPX, but a GPX keeps only the track, time, elevation and a few sensors. Repair the .fit file first: it keeps the laps, the device and the summaries.
Does FIT Rescue send my file to Strava?
No. Nothing is sent anywhere: you download the repaired file and upload it yourself.
Sources
Related guides
FIT Rescue tools
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