Garmin apps architecture ?

All of your account data (including activity data from the device) is stored on Garmin's servers. Your account (on Garmin's servers) is the common denominator which links your device to all of the apps and the website. Of course, Garmin devices are kind of unique (compared to Apple or Wear OS) in that you can use them without ever syncing with an account, but that's probably not a common use case.

I would say that if you could only use one app, it would probably be the Connect mobile app for Android/iOS. You'll find that especially on newer watches, there are features which can be accessed on the app and not the website.

The various apps allow you perform the following functions:

- sync account data (upload/download) between your device and Garmin's servers

- see your account data

Your watch can upload and download data to and from Garmin's servers via:

- Garmin Connect mobile app (iOS/Android) via bluetooth. In this case, your phone connects to Garmin's servers

- Wi-Fi (for watches which support it). In this case, the watch connects directly to Garmin's servers

- Garmin Express (PC/Mac) via USB cable. In this case, your computer connects to Garmin's servers

As a user, you can see your account data via:

- Garmin Connect mobile app

- Garmin Connect website

- Various 3rd-party sites or apps (like Strava) which can sync with your Connect account if you give them permission

4828874 said:

Also I don't understand what Garmin express is for. Is it only to make the transition between the watch and connect mobile?

You don't really need Garmin Express (or a computer) at all, since you can pair your watch to a phone via bluetooth and use the Connect app without ever opening Garmin Express or plugging your watch into a computer.

I think Garmin Express is a holdover from a time when there was no Garmin Connect mobile app. It may also exist for people who prefer not to sync with a phone or just don't have one. It can still be used to download large updates (like maps) faster than would be possible over wi-fi or bluetooth.

4828874 said:

What I understand is that connect mobile connects the watch via bluetooth, while connect web does not (why? it's a bit of a mystery.)

Correct, the website doesn't connect directly to your watch via bluetooth. My guess is Garmin probably thinks it isn't worth the development time to add this feature, since anyone who wants to sync via bluetooth can use the Connect app. Besides, the Bluetooth Web API is experimental, only supports BLE and is not even supported by every major web browser.

Another way of looking at it is if you were to use your watch exclusively with a computer (and not a phone), you would expected to use Garmin Express (or Wi-Fi) to sync, and the Connect website to look at your data. Here it makes sense for Express to be an application because it needs access to USB. And it makes sense for Connect to be a website since it has no need for the kind of things an application can do (direct hardware/filesystem access, high performance, etc.)

If you were to use your watch exclusively with your phone, you'd use the Connect app. Here it makes sense to just have one app for syncing and viewing your data since phone users have different expectations than computer users. (You can actually use the Connect website on a phone, but the user experience isn't very good.)

The website of course reflects any changes that were pushed to the servers. The website also has the ability to schedule data to be pushed to your watch on next sync. (e.g. You can create a workout or course on the website and schedule it to be pushed to your watch the next time your watch syncs via the Connect app, Wi-Fi or Garmin Express.)