Label decoder
Find the tiny grey text on your charger, power brick or appliance. Type the bit that says INPUT. Plugbert will tell you where in the world it's safe to plug in.
Examples:
Where's the label? On the charger brick, the bottom of the appliance, or molded into the plastic in tiny raised letters.
What matters? The INPUT voltage. "100-240V" is the magic phrase.
What doesn't? OUTPUT. That's what the charger sends to your device, and it's the same everywhere.