Since mid-September, Garmin has had a bug where some completely valid FIT files fail to upload.
This is a known issue, and below you’ll find my correspondence with Garmin support.
If you experience this, please report it to Garmin and include sample files. When you click this link, scroll to the bottom and select "Chat, Call, or Email"
I’ve already done so, but the more reports they receive, the sooner it may get fixed.
The tell-tale sign of this bug is that the error message appears instantly, before the file has a chance to upload to Garmin’s servers.
Work-around attempts
When this issue first appeared, it affected all files. Switching browsers (e.g., from Safari to Chrome) sometimes helped.
Now it’s more sporadic — apparently depending on the file itself.
For instance, I had one FIT file that Garmin refused to upload. I changed a single value (the first cadence point, from 39 → 40) — and then it uploaded perfectly!
No idea why that would make a difference.
As of this post, the issue is still ongoing.
//––– GARMIN SUPPORT CORRESPONDENCE BELOW –––//
Hello,
Thank you so much for that information! Garmin is aware of this issue our users are experiencing, and we are looking into this on our end as well. I would encourage the customers reach out and we can get them added to the case for this issue.
If you do have any other feedback or information, you can definitely submit to the link below. We are always looking for ways to improve our devices and platforms.
https://www.garmin.com/en-US/forms/ideas/
Thank you for choosing Garmin,
Alex
Product Support
Garmin International
For 24-hour access to support videos, manuals, FAQs & more, visit the Support Center.
My reply to Garmin (redacted):
Thanks.
This issue is ongoing. Previously, Garmin Connect would not upload any files from Safari — I advised users to try another browser. That seemed fixed briefly, but now the problem has returned for specific files.
The error occurs instantly, before the file could possibly upload — suggesting a front-end (JavaScript) validation error.
I’ve attached two nearly identical FIT files — one uploads successfully, one doesn’t. Both pass FIT SDK validation and third-party validators. Changing just one value in the file (for example, cadence 39 → 40) makes Garmin accept it.
Please ask your engineers to inspect any pre-upload JavaScript checks, as that’s likely where the bug originates.
Best regards,
[Name Redacted]
Garmin’s earlier response:
Hello,
Thanks so much for reaching out, I'm sorry you are having issues uploading those FIT files! Are you able to include one of the files and also answer the questions below pertaining to that specific activity?
– When did this occur?
– How often is this occurring?
– Did any issues occur when this activity was recorded?
– Are you able to view this activity on the watch’s history?
– Does this happen in different browsers?
Please submit the FIT file to the link below and let us know once done:
https://support.garmin.com/upload
Thank you for choosing Garmin,
Alex
Product Support
Garmin International
For 24-hour access to support videos, manuals, FAQs & more, visit the Support Center.
My original report (redacted personal info):
Hi,
I operate a website that helps users repair GPS tracks. Recently, several users reported that Garmin Connect rejects their FIT files. After investigation, I discovered that Garmin Connect was even rejecting files directly from Garmin devices.
Initially, switching browsers (Safari → Chrome) solved the issue. But now, some perfectly valid files still fail, even though all validators confirm they’re valid and other platforms (Strava, TrainingPeaks, etc.) accept them.
The strange part: if I change one small value in the file — like cadence 39 → 40 — it suddenly uploads fine.
The rejection happens instantly, before any backend validation could occur, so it appears to be client-side JavaScript validation.
I wanted to make Garmin aware of this, as users are assuming it’s an issue with my site — but the problem originates on Garmin’s end.
Product: Garmin Connect™
Summary: This appears to be a front-end validation bug in Garmin Connect that incorrectly rejects certain valid FIT files.
If you encounter it, please submit a report through Garmin’s feedback link above so it gets higher priority.