Electricity in Japan
Electricity in Japan 電気
The Japanese plug and socket are Type A: parallel flat two-pin (JIS C 8303, Class II), almost identical to the United States' standard plug and socket (NEMA 115 ).
However, whereas the two pins of many US plugs are of differing width, the Japanese plug and socket is unpolarized, meaning the slots in the sockets are the same size. A Japanese plug can therefore be freely inserted into a socket without worrying which pin is which.
Many appliances, especially those designed for travellers, are compatible with a wide range of voltages, from 100 to 240; so there should be no problem using such appliances in Japan as is. Most laptop computers are automatically multivoltage. Desktops may or may not have a manual multivoltage switch. Check with the manufacturer beforehand. Even if switchable, check if you an adapter for the plug.
The difference in voltage between Japan and North America is only about 10 volts, so North American products should be usable in Japan as is. However, appliances made for North America that produce heat, such as heaters, irons, hairdryers, etc. will not get as hot in Japan as they do in North America.
However, if your appliance has a three-prong plug, you will need an adapter for the plug to connect to the socket.
The use in Japan of a device designed solely for 240V should be avoided, unless you use a step-up transformer.