How to Choose a Prepaid SIM Card in Japan

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There are many prepaid SIM card brands for short term visitors to Japan and you may wonder how you are supposed to choose one from them. This post is for those who are not familiar with buying SIM cards. We will give some tips on how to choose a prepaid SIM card that is sufficient for your usage.

What is a SIM card?

A SIM card is a small chip you place in your mobile phone. It enables your phone to connect to the local network. Without it, your device is only able to connect to the internet via wi-fi.

What you should know when choosing a SIM card.

1. Size

There are three different sizes of SIM cards; Regular/Standard, Micro, and Nano. You can check what size fits on your device by looking up its specification on the internet.

2. [Data only] or [Data and Voice]

Most of the prepaid SIM cards are [Data only] SIM cards. It means it has no phone number, therefore you cannot make a voice call or use SMS. What you can do with a data only SIM card is to use the internet without wi-fi. You can use skype, WhatsApp, LINE, Facebook, Instagram, Google map, Gmail and everything you do on the internet.

At some airports, you can buy [Data and Voice] SIM cards. It is very strict in Japan to sell voice SIM and you cannot buy it from a vending machine. Also, it is more expensive than data only SIM cards.

3. Data amount

"1GB(1000MB)" , "3GB(3000MB)" ... those numbers on the package indicate the total amount of data you will be able to use with the product. Some products limit the data amount per day such as "110MB a day".

4. Period

Prepaid SIM cards have a fixed valid period. The date is counted from the day you activate it. There is a valid period such as 7 days and 30 days depending on the product. Once the service period is over, the SIM card no longer works.

5. Networks

Not all SIM cards in all parts of the world work on the same network. So, you have to check what networks the SIM card you are buying works on. Then, your device must be able to connect to those networks as well. If your device is unable to connect to the same networks as the SIM card's, it will not work.

6. Locked or Unlocked

When you buy a smartphone, you can choose either SIM-free, unlocked device, or a device locked to a certain carrier. To use a SIM card from a different company or country, the device must be unlocked. If you are not sure, you can ask the retailer.

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Tips

Do you need a phone number?

If yes, the choices are limited. We recommend you get one at the airport. Once you are out from the airport, it is very difficult to buy one.

You are not sure how much data you need?

Many providers let you check how much data you use every month. It will be helpful to know how much data you usually use and then choose a prepaid SIM that has the data amount you think is sufficient while you are on a trip. Also, you may want to check if the hotel you will stay offer a free-wi-fi. If they do, you will be able to save a lot of data since you will need the SIM card data only when you are outside the hotel..

Where to buy the prepaid SIM cards in Japan

There are SIM card vending machines in the major airports. Some of the machines only accept credit card and some only cash. There are counters at the airport that sell prepaid SIM cards and some convenience stores may have them, too, but be aware that those shops are not open 24h. Other than in the airports, large electronic retailers such as Bic Camera and Yodobashi Camera in city centers sell them. However, if you are going to stay outside city centers, it may be difficult to find them once you are out of the airport.

1GB/30days, what does that mean?

That means the card will be active for 30 days period of time from the day you activate it, and you will have 1GB data amount to use. Once you finish using 1GB, the device will no longer be able to connect to the network or the speed will be very slow. Once the card is expired, even if 1GB is not finished, the card will be inactive.

You may be able to top-up the data amount but you cannot extend the validity period.

Some prepaid card brands sell coupons to top up the data amount and some allow you to recharge the data amount from the website. However, you cannot change the validity period.

Not all devices work with SIM cards in Japan

If the networks of the SIM card and your device are not compatible, it will not work. However, prepaid SIM cards are non-refundable. We have posts on how to check the compatibility, please check the following posts: How to Check if your iPhone Works with SIM Cards in Japan, How to Check if your Android Phone Works with SIM Cards in Japan. Some shops offer a test SIM card which you can try before you buy. Also, CDJapan Rental's rental SIM cards are refundable if it does not work with your device.

Coverage of the SIM card

Your device must be able to connect to all of the bands(networks) that the SIM card use for the best result of the coverage. Currently, all short-term prepaid SIM cards use Docomo network, therefore the coverage is the same for all SIM cards. However, the quality and the speed could be different depending on the product. You may want to check the reviews.

Rent a mobile wi-fi

If your device seems like it is not compatible with the SIM card network, consider renting a mobile wi-fi. You can rent a mobile wi-fi in Japan and it will work with any wi-fi enabled devices.


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