Tokyo Data SIM Guide: The Carrier With the Best Speed and Signal

Japan is Taiwanese travellers' No.1 favourite destination, drawing millions of visitors from Taiwan every single year.

When it comes to travelling in Japan, Tokyo is easily one of the most popular cities — so how do you buy a Tokyo data SIM that keeps you online smoothly, without hitting lag issues while there?

Today's article breaks down Tokyo's internet speed and compares Japan's 3 major carriers, so you can choose the right Tokyo data plan with confidence!

Is Tokyo's internet fast?

How is the internet speed in Tokyo, Japan? Is it too slow, or is signal generally poor?

According to the UK-based network speed monitor OpenSignal, Tokyo's average download speed sits at 204Mbps.

For comparison, Taipei's average speed is 224Mbps — so Tokyo runs a touch slower than Taipei overall, though the gap is not huge, meaning Tokyo's internet should feel roughly comparable to what you are used to in Taipei.

Comparing Japan's 3 major carriers

In Taiwan, we all know the major carriers as Chunghwa Telecom, Taiwan Mobile, and FarEasTone — so which carriers are best known in Japan, and how do they differ from each other?

Japan carrier 1: NTT DoCoMo

NTT DoCoMo is a publicly listed Japanese carrier that has operated for over 20 years, with the longest history and the largest user base among Japan's carriers — comparable to Chunghwa Telecom in Taiwan. Its coverage is comprehensive, with signal reachable almost anywhere in Japan.

Looking at NTT's coverage map below, nearly every major city in Japan gets 4G or better signal, and Tokyo especially is almost entirely covered by 5G.

Japan carrier 2: SoftBank

SoftBank is not a bank at all — it is a major Japanese mobile carrier, part of a group spanning telephony, internet and technology services. Coverage is strong in big cities, though somewhat less stable in mountainous or rural areas. Overall, it is a stable, quality carrier.

Note: SoftBank does not provide a public coverage map for reference.

Japan carrier 3: au (KDDI)

au (KDDI) is a newer carrier formed from the merger of au and KDDI, one of Japan's three major carriers. Its overall coverage is somewhat less consistent than the other two carriers above, sometimes losing signal indoors, but coverage still remains fairly strong overall, and there is definitely no issue in major cities like Tokyo or Osaka.

Recommended Tokyo data SIMs

By this point, you should have a good grasp of Tokyo's internet speed and Japan's carriers, so getting online during your Tokyo trip is nothing to worry about.

But here is the real question: which Tokyo data SIM, or Tokyo SIM card, should you actually buy?

Here is a look at the different Tokyo SIM plans offered by DJB, a company specialising in travel data SIMs:

Recommended Tokyo SIM	DJB Daijobu Unlimited/Daijobu Unlimited Plus	DJB Daijobu Travel	DJB Daijobu Play	DJB Reiwa Card
Carrier	NTT Docomo/SoftBank/au (auto-detects on insert, no setup)	NTT Docomo/SoftBank/au (auto-detects on insert, no setup)	NTT Docomo/KDDI	KDDI
Data	Unlimited, no throttling (Plus reaches up to 300Mbps)	500MB/1GB daily, throttled after cap	Unlimited, no throttling	Unlimited, no throttling
Calls included?	No	No	No	No
Can share as hotspot?	Yes	Yes	Yes	Yes

Looking at what is available now, the vast majority of Tokyo SIM plans automatically detect the carrier once inserted, and mostly run on Japan's three major carriers — so you do not need to spend much time researching which carrier to pick when buying a Tokyo SIM.

We can also see that all of these Tokyo SIMs offer unlimited data — apart from Daijobu Travel's daily data cap, every other plan is genuinely unlimited with no throttling — so whether you are a light or heavy data user, any of these recommended Tokyo SIMs will suit you well.

One important thing to note: Tokyo data SIMs cannot make calls to mobile or landline numbers (calls through apps like LINE are unaffected), but you can still share the connection as a hotspot for others.

If you have any questions about Tokyo SIMs, or are not sure which to choose, feel free to reach out — our team is happy to help you find the Tokyo data option that best fits your needs!

Further reading:
>> 2024's most recommended Japan coupons, all in one place — just screenshot to save at Don Quijote, Matsumotokiyoshi and more
>> 2024's best Japan travel apps: the complete guide to travel, transport and map apps every traveller loves
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