Which way should be on for a switch?

In the USA and Canada and Mexico and the rest of North America, it is usual for the "on" position of a toggle switch to be "up", whereas in many other countries such as the UK, Ireland, Australia, and in New Zealand it is "down." ...

1. Is the I or O on?
2. Which is on and off on a switch?
3. Does it matter which way you wire a switch?

Is the I or O on?

(1 or | means on.) IEC 60417-5008, the power-off symbol (circle) on a button or toggle, indicates that using the control will disconnect power to the device. (0 or ◯ means off.) IEC 60417-5009, the standby symbol (line partially within a broken circle), indicates a sleep mode or low power state.

Which is on and off on a switch?

Power buttons and switches are usually labeled with "I" and "O" symbols. The "I" represents power on, and the "O" represents power off.

Does it matter which way you wire a switch?

Because the switch terminals are interchangeable, it doesn't matter which wire you put on each.