Read the input specification
Look at the power supply or appliance for its supported input voltage and frequency. Do not confuse the charger's output to a phone with its input from the wall. Some modern chargers support a broad input range, but that does not mean every item in your bathroom or camera kit does.
Apple, for example, states that its USB power adapters support 100–240V AC at 50–60Hz. That is information about those adapters, not a blanket rule for every charger. Read your own model's label and official instructions. If the print is unreadable or the specification is unclear, resolve it before plugging the item in abroad.
Match the plug and the load
Identify the plug arrangement used at your destination and choose an adapter suitable for the equipment. A multi-country device may be convenient, but its listed ratings and grounding arrangement still matter. Do not defeat a grounding connection or stack loose adapters to make an incompatible plug fit.
High-power appliances such as hair dryers need particular care. A small adapter intended for charging electronics may not be suitable for them. Ask the manufacturer what is required or use an appropriate appliance provided at the accommodation. A voltage converter is a separate device with its own compatibility limits, not an automatic cure for any mismatch.
Rehearse the charging setup
Connect the charger and cable at home where compatible and confirm that the intended device charges normally. Inspect for damage, loose pins or frayed cables. Avoid using equipment that is damaged, unusually hot or otherwise behaving abnormally. Follow the manufacturer's safety instructions rather than trying to repair a travel accessory during the trip.
Think about the physical shape as well as the electrical specification. A heavy universal adapter can be awkward in a recessed or loosely positioned socket. Plan a stable arrangement without blocking other sockets or leaving a cable stretched across a walkway. Taking one appropriate, tested setup is more useful than carrying several adapters whose ratings you have not checked.
