Tapiriik. It will synchronize activities from Garmin Connect to Strava with a single click, or if you're willing to pay $2/year it will do it automagically.
I use www.copymysports.com. From memory it was basically just a case of making the initial connection, then it uploaded in bulk and all new uploads appear automagically after that. I had to re-create the initial connection after 6 or 7 months of use, but it has been fine since.
Here is another plug for www.copymysports.com I've used it for about 6 months, had to re-create the connection once as listed above (I believe this was during an update to either copymysports or garmin connect, don't remember which). It has worked fine ever since and it seems the lag time from the time you upload your activity to Garmin to when its copied over automatically to Strava has reduced significantly in the past month. It now seems to happen within 30 minutes to an hour where it used to take up to 4 hours or longer when I originally started using it.
I have moved to just doing it manually again, I noticed yesterday that on one ride alone when I used Tapiriik to sync I lost 1,000ft+.
I'm no real climber so am never too fussed but as I'm doing Rapha rising this year losing 1,000ft+ off a 5,000ft ride is annoying. I deleted the ride and loaded it straight from my 810, the elevation then matched the 810 (and also GC's value).
Other than that I think it's a real good sync tool. Jay
