for pc, use obs. for mobile, download a screen recorder and use the everyplay airplane mode trick.
Wtf is the everyplay airplane mode trick like wtf the fuck????????????????????????? 🙂🙂🙂🙂🙂🙂🙂🙂
so there are tons of screen recorders for phones that you can use to record gd, but it usually causes a lot of lag and it becomes really hard to play. there used to be an in game tool called everyplay which you could use to record completions, but it was taken offline in 2018. however, you can still use it if you have another screen recorder involved (any is fine).
first, enable everyplay recording in gd settings, and then play whatever level you want to record. once you beat it, on the level completion screen, you'll see a button that says "watch replay". nothing will happen if you click it (you'll just get an error message). however, if you set your phone to airplane mode, and then click it, it will show the replay of the level completion. so you can use the screen recorder to record that replay, and then turn off airplane mode.