Hi @David , I’ve done a detailed byte-level analysis comparing original Garmin FIT files against the same files exported by Intervals.icu. I found several issues I wanted to report with concrete evidence. Before anything else — if I’m missing something obvious or there’s already a known workaround …

Did you read that? [image] Garmin FIT fields not coming in Bug Reports Unfortunately Garmin now does some filtering on the files they return via the API. The file is not the same as what you can download manually from Garmin Connect or what is included in the GDPR file whe…

[image] R2Tom: Did you read that? Yes, I read that! In my case though, I’m not syncing via Garmin API — I export my data from Apple Health using HealthFit. In the original FIT file the running dynamics records are all there, but when I download the modified version from intervals.icu (not th…

[image] JDE: but when I download the modified version from intervals.icu (not the original) I don’t understand - did you download the Original Fit File or the one from intervals after analyzing? [image] Because, if you didn’t download the original fit file, it should obviously not be the o…

[image] R2Tom: I don’t understand - did you download the Original Fit File or the one from intervals after analyzing? [image] Yes, I downloaded both — the original FIT file and the one processed by intervals.icu — and there are clear differences between them. Here’s my typical workflow: I …

Actually, I know I can already do something similar workflow with fitfiletools.com — but the whole point is that doing it directly from intervals.icu would be much more streamlined and flexible. Being able to edit the binary FIT data straight from the platform is really powerful: it lets you fix val…

That’s not supported. There’s only basic data in the intervals exported FIT.

Hello, @MedTechCD , yes and no. I mean fair point — but that’s actually where the issue lies. Custom fields and streams added to an activity are already included in the downloaded FIT file, but they come out as developer fields (dev_fields) instead of being mapped to their proper standard FIT SDK eq…

It’s not supported at this time, so it’s not a bug. Put it in Feature requests.

[image] JDE: I export my data from Apple Health using HealthFit. In the original FIT file the running dynamics records are all there, but when I download the modified version from intervals.icu (not the original) Clarity required. What;s your original source data? A Garmin Device? Apple Watch…

[image] JDE: f a custom field or stream name matches a known FIT SDK standard field name, export it using the correct standard global message and field number rather than as a dev_field The Intervals.icu generated fit file is created from the processed data in Intervals.icu. So stuff that did…

Export: a Intervals.icu FIT vs Dowload Original FIT

Bug Reports

R2Tom 12 March 2026 19:09 2

Did you read that?