United Kingdom vs Japan do you need an adapter?

Japan and the UK are opposites on the global voltage scale. Japan uses 100V — the world's lowest, found nowhere else — while the UK uses 230V. Japan uses flat Type A/B blades (like the US), while the UK uses the large rectangular Type G. These are incompatible on every dimension: different plug shape, completely different voltage (less than half), and different frequency (Japan: 50Hz east / 60Hz west, UK: 50Hz). Despite the lower voltage, most modern devices from the UK handle Japan's 100V fine because they're rated for the full 100-240V range.

Japan's 100V standard was adopted from early American Edison DC systems in the late 19th century and was never upgraded, unlike Europe and Australia which moved to 220-240V for efficiency. The UK developed its distinct Type G through post-WWII safety-focused design standards. Japan's split between 50Hz (eastern Japan, including Tokyo) and 60Hz (western Japan, including Osaka) is a unique quirk from importing both German (50Hz) and American (60Hz) generators in early electrification.

UK travelers to Japan: you need a Type G to Type A/B adapter. Your UK phone charger, MacBook, and most electronics will say '100-240V' on the brick — they handle Japan's 100V perfectly. What to watch: hair tools at 230V-only specification rated for UK power will work at reduced wattage (charge slower, heat less) at Japan's 100V rather than failing — but run cooler than expected. UK-purchased hair dryers at 1800W will output significantly less heat in Japan. Japanese hotels almost universally provide hairdryers anyway. Eastern Japan (Tokyo) runs 50Hz like the UK; western Japan (Osaka, Kyoto) runs 60Hz — irrelevant for most modern devices.

Japan's flat Type A sockets are the same as US sockets but the voltage is different (100V vs 120V). UK travelers get an unusual benefit: if a US traveler is also in your group, their American adapter works for Japan too. Japanese convenience stores (7-Eleven, FamilyMart, Lawson) sell basic adapters but Type G-to-Type A is less common than in major electronics stores (Yodobashi Camera, Bic Camera) in Tokyo and Osaka.