When I left click it right clicks
I was playing Minecraft and it happened
MacBook Air 13″, macOS 10.15
Question marked as
Check your System Preferences => Mouse, if you are using a mouse, and Trackpad if you are using a trackpad. Right and left click locations/sides are specified there. If those look correct, check your Minecraft preferences.
If all the settings look correct, and it remains a mystery still, try restarting and boot into Safe Mode (Shift key held down, takes 10-15 minutes possibly). Then reboot normally and retest.