Not sure what is wrong with the script, JumpRequest is being fired sometimes more than once.
CanDoubleJump = false
LastJumpTick = tick()
game:GetService("UserInputService").JumpRequest:Connect(function()
if CanDoubleJump == false then
CanDoubleJump = true
elseif CanDoubleJump then
if tick() - LastJumpTick <= 0.5 then
print("DOUBLE JUMPED!")
end
CanDoubleJump = false
end
LastJumpTick = tick()
end)

2 comments
i put this into a local script in StarterCharacterScripts and it works fine doesn't print twice
It works only when u press spacebar in intervals, if you hold spacebar it will print multiple times.