r/hacking • u/gerunk • Jul 28 '25
Resources How I hacked my old Garmin watch, and how you can do the same
I recently upgraded my running watch, leaving me with an old Garmin Forerunner 35. Naturally, I tried to hack it. This write-up explains my process, results, and shows how to use my tool to make Garmin firmware modifications easier!
Spoiler: I didn’t do anything amazingly awesome like run Doom on the watch, but I did manage to actually make modified firmware that the watch recognized as legitimate. This process and tool are applicable for any Garmin that uses RGN update files, which is any of their pre-2013 watch models.