Well, first off it depends on which type of Garmin device you have, see below:
Garmin Handheld Devices:
These include the Etrex, GPSMap, Oregon, Montana, Monterro, etc.
For these models you have multiple ways to copy a GPX file to the device, these include:
- Dragging and dropping the GPX file to the GPX folder (under the GARMIN folder) on either the internal storage, or a MicroSD card. You can also use Copy and Paste instead.
- Using the Send to Device option in Garmin Basecamp (after selecting the route/track/waypoints that you want to send to the attached Garmin device).
Garmin Smartwatches:
These include the Epix, Fenix, ForeRunner 945, MARQ, Tactix and related models
For these models you have multiple ways to copy a GPX file to the device, these include:
- Dragging and dropping the GPX file to the NewFiles folder (under the GARMIN folder) on the internal storage, of the device You can also use Copy and Paste instead*.
- Using the Send to Device option in Garmin Basecamp (after selecting the route/track/waypoints that you want to send to the attached Garmin device).
- If you have imported the GPX file in to Garmin Connect (on your phone), you can also use that to transfer it to the Garmin.
[*] There is an extra step required to see the Fenix/Epix or some of the new Edge models on your Mac; this being the need to use AndroidFileTransfer to be able to see the file system (folders) on the watch.
You can also use Garmin Explore, Komoot, OutdoorActive, OS app, and so on to transfer the GPX file to your watch or other connected Garmin device via your phone.