low = 100–127 V and high = 220–240 V. An adapter is flagged when no origin plug type seats in a destination socket (with two travel exceptions: Type A seats in Type B; a Type C europlug usually seats in E/F and several other round-pin plates). A voltage converter is flagged when the origin band and destination band differ (low vs high). Same type family and same band → neither. This is a lookup, not a live measurement.
Pick a country to see the wall plate, or compare the plug you already have with where you are going. Dual-voltage USB bricks almost always need shape only. Hair dryers, kettles and irons often need a real transformer if the voltage band changes.
Original line drawings of the pin layout (plug face). Not photos, not a third-party sheet.
An adapter only changes the pin shape so the plug seats in the wall. A voltage converter (or a transformer) changes 100–127 V to 220–240 V or the other way. If the pin family matches and both countries sit in the same voltage band, you need neither. Dual-voltage USB chargers usually need an adapter only. Single-voltage hair dryers and kettles often need a converter as well as an adapter.
Most USB phone, laptop and camera chargers are dual-voltage (look for 100–240 V ~ 50/60 Hz on the brick). In that case you only care about pin shape: if the origin and destination types do not overlap, pack an adapter. The charger still has to be the one you already own — this page does not certify a specific model.
Usually yes for unearthed, low-current devices. Type C was designed to sit in many European round-pin plates, including E and F. It does not earth the appliance and it is not a high-power connector. Grounded Type E or F appliance plugs are a different story and may need a matching adapter.
No. Shapes and voltages here are typical public facts for travellers. Hotels, older buildings and multi-standard plates vary. An adapter is not a voltage converter. High-power appliances need a transformer or dual-voltage gear. MultiSwitch is not electrical advice and not a certification body.