Discussion - Recent Threads

Rust #![no_std] library for decoding and encoding FIT files

muktihari — Mon, 25 May 2026 06:27:06 GMT

Hi, I created a Rust library for decoding and encoding FIT files with #![no_std] support, making it portable across a wide range of environments; from baremetal, WebAssembly to server applications, and potentially mobile platforms such as Android and iOS as well. The library is designed to work in baremetal Rust, where performance and memory efficiency are carefully considered.

Repository: https://github.com/muktihari/rustyfit

I originally started this project to learn Rust, and also because the official FIT SDK currently does not support Rust. I previously built a FIT library in Go (https://github.com/muktihari/fit), so I thought it would be interesting to do a Rust version as well. I Hope it could be useful for others working with FIT files in Rust ecosystems.

The project is open source and still evolving, so feedback, bug reports, and contributions are very welcome.

If companies or teams using Garmin FIT technologies need assistance integrating or extending it, I’d also be happy to collaborate professionally.

And of course, if Garmin is ever interested in making this capability official or collaborating on maintenance, I’d be excited to discuss that as well.

v21.205 of the JavaScript SDK added type definitions.

Ben FIT — Tue, 19 May 2026 21:46:23 GMT

v21.205 of the JavaScript SDK added type definitions.
https://github.com/garmin/fit-javascript-sdk/tree/main/src/types

Along with the types definitions, the decoder now adheres to the profile for array fields.

Array fields will always be returned as arrays, even when there is only one element
Non-array fields will always return a single value, even when there are multuple values

The binary protocol allows for any field to be an array, whereas the profile provides an unenforceable contract of what fields are arrays. That is true for all SDKs.

Previously, the JavaScript SDK would decode a field and then check the array length. If the length as one, then it would return the value at index zero, else it would return an array.

We did not want to carry that behavior forward when adding the type definitions. So now, the decoder references the profile to see if a field is an array or not and returns an array or scalar based on the profile.

While this change has the potential to be a breaking change, we don't think it will. The reason being is, most people should have discovered by now that sometimes a field that was not expected to be an array might be. i.e. any string field and any field with a name that starts with "enhanced", and everyone should have checks in their code to handle this. If so, then that defensive code can be removed.

If this change does break your code, the read() method of the Decoder class has a new legacyArrayMode option. The default is false. Setting the option to true will revert back to the previous behavior. The v21.205 release did not include many profile changes, a few product ids, so the other option is to stay with 21.202 and update to 21.205 at a later time. The new legacyArrayMode option is marked as deprecated since we plan to remove it by EOY26.

Even if you do not use TypeScript, the type definitions should provide better auto-complete and context sensitive help when using the JavaScript SDK.

como faz para ser um desenvolvedor

2190895 — Thu, 14 May 2026 18:22:00 GMT

eu trabalho com programação e recentemente fiz um programa de corrida e preciso ser um desenvolvedor para pega algunhas informações

Parsing transitions in multi-sport FIT files — best practice?

Sébastien DONVAL — Thu, 14 May 2026 06:01:45 GMT

Hi all,

I'm building the activity ingestion layer for Triscale.eu, a multi-sport coaching platform (triathlon, cycling, running) based in France. We're preparing to receive .FIT files from athletes via the Garmin Connect Activity API once our Developer Program access is approved.

Quick question on multi-sport file structure: when an athlete records a triathlon as a single multi-sport activity (swim → T1 → bike → T2 → run), what's the recommended way to identify the transitions in the FIT file?

From what I've read so far, it looks like multi-sport sessions are exposed as a session per sport with sport_type changes, but I'd like to confirm two points:

- Are transitions (T1/T2) emitted as their own session, or as a gap between sport sessions?
- Is there a recommended message type or flag to differentiate "real" sport segments from transitions for downstream analytics?

If anyone here has built triathlon-aware parsing on FIT files, would value a pointer to your approach.

Thanks,
Sébastien D.
Triscale.eu — multi-sport coaching platform, FR

Obj-C SDK: negative sint32 developer field values return 0

krooneywa — Mon, 11 May 2026 23:33:03 GMT

In the Obj-C SDK, FITDeveloperField.getValueFor(0) returns 0 for developer fields with base type sint32 (0x85 / 133) when the value is negative. Positive sint32 values decode correctly on the exact same code path. Java SDK (via FIT CSV Tool and fitfileviewer.com) reads the same files correctly, including negatives.

Same field name (calibration on device_info), same base type, same SDK build — only the sign differs.

Reading code (called from a MesgListener):

SWIFT EXAMPLE

let name = devField.definition.getFieldNameforIndex(0)
let rawNumber = devField.getValueFor(0)
let baseType = devField.definition.getFitBaseTypeId()
print("name:\(name ?? "nil") rawNSNumber:\(rawNumber) baseType:\(baseType)")

Output:

// File with negative values on disk (e.g. -45 per Java SDK):
dev field — name:calibration  rawNSNumber:0  baseType:133
dev field — name:calibration  rawNSNumber:0  baseType:133

// File with positive values:
dev field — name:calibration  rawNSNumber:108  baseType:133
dev field — name:calibration  rawNSNumber:107  baseType:133

Looks like the sint32 path isn't sign-extending — values with the sign bit set get clamped to 0 instead of returned as negative. Worth checking sint8/sint16/sint64 too.

Happy to share test files. Thanks!

FIT SDK C# changes field base type in some fields

9881454 — Mon, 11 May 2026 16:34:13 GMT

Hi,

I'm re-encoding fit files to add extra data. For some reason, after 20+ reencodes, I'm now debugging an issue with producing invalid files.

I noticed that the C# SDK changes the field base type, at the very least since I didn't check every other field base type, on the FieldIdMesg definitions,

during the decoding process. So the FitMessages produced, already have a different field base type for some field definitions.

For example, the original file has uint16 data type (value: 4) for Manufacturer, Product and Number and uint32(value: 6) for TimeCreated.

But, during decoding of the file, the parser looks up predefined `Mesg` definitions for FileId messages, created here:

https://github.com/garmin/fit-csharp-sdk/blob/5462684d8f34aaea1d36b2fd5b134f732bc2ec9b/Dynastream/Fit/Profile.cs#L853

For some reason, the base data type is set to 132(0x84), which is ExdQualifiers. Does anyone know what that is?

And why it's changed like that?

Recherche profil activité: VTT DH ou Bike Parc

4111861 — Mon, 11 May 2026 09:09:05 GMT

Salut à tous! le choix d'activités proposés est énorme mais, je pratique le VTT DH et il y a pas cette activité (incroyable..) Du coup, je mets en ski comme ça, ça enregistre que les déscentes. Bref, y a t'il des deamndes pour obtenir de la part de Garmin l'activité VTT descente ou MTB DH ou Bike Park? merci

equipment

helmutfritsche — Sun, 03 May 2026 13:02:29 GMT

hi there,

how can i get the equipment (e.g. shoes) for an activity using the SDK?

Data field pace for edge 530

AndiPl — Sat, 02 May 2026 16:35:23 GMT

Dear All,

I am not used in programming but would like to have a data field pace for my edge to add to a training page (bycicle).

I guess it's not as duffucult so I am asking if somene would support me.

Greetings and many thanks in advance

Andreas

Developer onboarding blocked

Noah — Wed, 29 Apr 2026 13:19:37 GMT

I have emailed connect-support@developer.garmin.commultiple times with no response. The developer onboarding form has been down for more than a month. Has anyone had any success recently onboarding to the developer account or getting access to the activity API?

When I sleep in two phases, I can only access the data for the second phase of my sleep. Consequently, I cannot view my complete sleep data.

7857383 — Mon, 27 Apr 2026 09:50:19 GMT

When I sleep in two phases, I can only access the data for the second phase of my sleep. Consequently, I cannot view my complete sleep data.

help

6640688 — Fri, 24 Apr 2026 15:12:00 GMT

ciao! il mio edge 530 si è bloccato durante lo stand-by e il file .FIT risulta corrotto. i siti online non riescono a ripararlo. qualcuno può aiutarmi?

Hi! My Edge 530 froze during standby and the .FIT file is corrupt. Online sites can't fix it. Can anyone help?

API approval time

2131611 — Thu, 23 Apr 2026 04:18:31 GMT

Hi,

I submitted our API access request 7 weeks ago. Within a few days, I received an email stating that the request had been received and that the process would take up to two weeks. The message also mentioned not to send reminders.

How can I get update on the current status of the request? I did try sending one follow-up earlier but have not received a response.

Hey, I currently develop a fitness app for iOS and would like to get access to the module for live heartrate data in Garmin Connect to send the data to my app and show it there. Do you maybe know if and how this is possible? Best Regards Otto

2593697 — Tue, 21 Apr 2026 13:51:54 GMT

fitness app for iOS

Max Graph (or Date Ranges)

9848032 — Tue, 21 Apr 2026 06:07:32 GMT

Hi.

Is it possible to providea graph of for all time since the Garmin was first used?

In addition to the Monthly and Yearly Graphs, show a Max graph, or at least Date Ranges.

I'd be very keen to see how my stats look over the last six years since I first purchased it?

Conor

Persistent 429 on API login — account blocked for 48+ hours

ickerc — Tue, 21 Apr 2026 04:03:34 GMT

Hi, I'm building a personal training planning tool that reads my own Garmin Connect data (activities, daily wellness, sleep) using python-garminconnect v0.3.1.

After a few failed login attempts during initial setup, my account is now returning 429 on every API login attempt — for 48+ hours and counting. My account works fine on the web and mobile app. No MFA enabled. No rate-limit email from Garmin.

Error across all strategies:
- `portal+cffi`: Portal login returned 429. Cloudflare is blocking this request.
- `portal+requests`: HTTP 403
- `mobile+cffi`: HTTP Error 429
- `mobile+requests`: Login failed (429 Rate Limit)

I've tried different IPs (home WiFi + mobile hotspot) — same result. The block appears to be at the account level, not IP.

Has anyone found a workaround when in this blocked state?

Any help appreciated.

How do I access my .fit files

8985916 — Sat, 18 Apr 2026 13:40:54 GMT

So my watch died towards the end of my run and therefore the run didn't sync to my garmin connect account. I've read online that I might be able to recover it from a .fit file but I don't know how to find them on my computer. Can anyone help please?

Georgian language

4418724 — Sat, 11 Apr 2026 09:51:02 GMT

Hello guys, please add Georgian language or at least font to receive readable messages. Common guys such a expensive watch and no support. Garmin fenix 8 51 solar user.

Getting Developer Access

8960612 — Thu, 09 Apr 2026 22:52:44 GMT

Hello,

I am pretty deep into developing an app, but I'm unable to request access to the developer program / APIs as the website is down.

Is there an email I can contact to submit the request?

Téléchargement des fichiers .FIT

pierrevey — Fri, 03 Apr 2026 18:24:21 GMT

Je possède une FENIX 8, parfois lorsque j'upload mon activité via WIFI ou BLUETOOTH mon activité ne s'affiche pas /Garmin. Elle est pourtant ok sur la montre, pas de bug apparent. J'ai également tenté de récupérer le fichier .FIT et de l'uploader directement via GARMIN CONNECT (/windows je précise). et là, même constat, cela ne fonctionne pas. Qq'un a t'il le même problème? Merci

Téléchargement des fichiers .FIT

pierrevey — Fri, 03 Apr 2026 17:55:18 GMT

Guidance on obtaining Product ID for FIT File (Mfg.ID already assigned)

7505646 — Fri, 03 Apr 2026 03:45:08 GMT

Hello Dear FIT Developer Support Team,

I hope you are doing well.

We are a wearable device manufacturer and have recently been assigned a Manufacturer ID through the ANT+ program. We are currently integrating FIT file generation for our devices and preparing for compatibility with platforms such as Strava.

During implementation, we understand that the FIT file requires both a Manufacturer ID and a Product ID (e.g., within the Device Info message). While we have our Manufacturer ID, we would like to clarify the correct process for obtaining an official Product ID for our device(s).

Specifically, we would appreciate guidance on the following:

What is the proper process to request or register a Product ID?
Should this be done through ANT+, Garmin FIT, or another channel?
Are Product IDs assigned per device model/SKU?
Is there any required information or documentation we should prepare in advance?

Our goal is to ensure that our FIT files follow official standards and that our devices are correctly identified across platforms.

Thank you very much for your support. We truly appreciate any guidance you can provide.

Best regards,

Jiyuan

** Column D "Value" is what I mean for the Product ID.

Suggestion: Show estimated recovery date and time (not only hours)

1181255 — Mon, 16 Mar 2026 12:30:43 GMT

Hello,

I would like to suggest a small improvement regarding the Recovery Time metric shown after workouts.

Currently, Garmin devices display recovery as a number of hours (for example: 38 hours). While this is helpful, it could be even more practical if the device or app also showed the estimated date and time when full recovery is expected.

For example:

Current time: 16 Mar 2026, 14:00
Recovery time: 38 hours

Instead of displaying only 38h, it could also show something like:
Estimated full recovery: 18 Mar 2026, 04:00

This would make it much easier for athletes to plan their next training session without having to manually calculate the time.

If such a feature already exists in FIT SDK fields or Garmin APIs, I would appreciate any guidance. Otherwise, it might be a useful enhancement for future updates.

Thank you!

Import data from Chinese account to International account

2966390 — Fri, 13 Mar 2026 04:47:03 GMT

Hi, I have recently switched from a Garmin China account to a Garmin international account. I lived in China for 8 years hence the Chinese account. I now moved to Malaysia and have always stayed on the Chinese account, until recently after I received an email that I had to update my phone number. This had to be a Chinese number but I don't have one anymore. Garmin Support suggested to switch to an international account instead. I have downloaded all my data, created a new international account with another email address and tried to import the data from the Chinese account. This doesn't work unfortunately. It doesn't matter if I try all at the same time, or just one at a time. Support has looked into it and now say they can't help me any further. So that is just it then...? That's very disappointing. I had a streak of 1301 days of >10k steps a day which is now then lost? Is there anyone here that knows the trick? To be fair I am not worried about the activities itself - I just would like my streak back. Thanks a million!

Discrepancies Between FIT Files from Garmin Connect and API (API Downgraded?)

pepe — Thu, 12 Mar 2026 15:50:17 GMT

Unfortunately, Garmin now applies extensive filtering to the files they serve via their API. This means the file retrieved through the API is not identical to:

The file you can manually download from Garmin Connect

What's being filtered?

Garmin used to strip out workout steps from API-delivered files. However, based on recent observations, it appears Garmin have recently expanded extensively this filtering to include additional data elements—likely explaining the missing of several message numbers, session and lap fields we're now seeing.

Discussion - Recent Threads

Rust #![no_std] library for decoding and encoding FIT files

v21.205 of the JavaScript SDK added type definitions.

como faz para ser um desenvolvedor

Parsing transitions in multi-sport FIT files — best practice?

Obj-C SDK: negative sint32 developer field values return 0

FIT SDK C# changes field base type in some fields

Recherche profil activité: VTT DH ou Bike Parc

equipment

Data field pace for edge 530

Developer onboarding blocked

When I sleep in two phases, I can only access the data for the second phase of my sleep. Consequently, I cannot view my complete sleep data.

help

API approval time

Hey, I currently develop a fitness app for iOS and would like to get access to the module for live heartrate data in Garmin Connect to send the data to my app and show it there. Do you maybe know if and how this is possible? Best Regards Otto

Max Graph (or Date Ranges)

**Persistent 429 on API login — account blocked for 48+ hours**

How do I access my .fit files

Georgian language

Getting Developer Access

Téléchargement des fichiers .FIT

Téléchargement des fichiers .FIT

Guidance on obtaining Product ID for FIT File (Mfg.ID already assigned)

Suggestion: Show estimated recovery date and time (not only hours)

Import data from Chinese account to International account

Discrepancies Between FIT Files from Garmin Connect and API (API Downgraded?)

Persistent 429 on API login — account blocked for 48+ hours