Polar is in its own world, although some websites, like TrainingPeaks, will accept Polar data. Everyone else is supposed to live in the .FIT file world and thus those files should be importable into any website or software other than Polar. That said, there's a current screwup going on between .FIT formats, FIT 1 and FIT 2. Some equipment now creates FIT 2 files which don't import into some websites or software.which only accept Fit 1 files. I haven't encountered this problem since my Edge 800 uses old firmware, though problems with Wahoo files produced by new firmware have been noticed. I doubt that we'll see any problems with Garmin devices. There's a FIT File Repair Tool that fixes FIT 2 files for import.