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How to check whether your phone is sim-lock device

sim lock phone

this article was originally posted on facebook by JP Smart SIM.

Mobile phone landscape in Japan is a “different world”

Previously, while people in countries around Asia and Europe has been familiar with sim-free (or called as open-line) device, cell phones used to be very restricted in Japan. It was nearly impossible to bring your phone into Japan and use it on one of the Big-Three networks (Docomo, Au, and Softbank). If you didn’t buy one of the company’s phones on an overpriced two-year plan, then you couldn’t get access to its network.

Thankfully, this all changed a few years ago, when the evolution of MNVOs brought an end to the restrictive practice that was the blanket ban on phone unlocking in Japan. People now can freely choose a cheaper plan or transfer to another reasonable carrier without stuck in the heavily restricted 2-year-contract.

For newcomers to Japan who have non-experience on Japanese stuff, they often seek and buy old phones themselves via Facebook or 2nd hand shops selling old phones (shop owners are mostly foreigners). So they are easy to get cheated to buy the lousy device which is blocked by the network operators. These devices are usually much cheaper than unlocked devices.

Thus, in this article, we will guide you on how to check the phone sim-lock status of all carriers.

Steps to check if the phone network is blocked

STEP 1: Find the IMEI code of your device (Japanese called 製造 番号 – Seizoubangou): you can use either of the following two ways:

  1. Dial the phone call *#06#, the device will display a sequence of about 14 ~ 15 characters, this is the IMEI code of the device.
  2. Find the IMEI number in the “Settings” of your phone
  • For iPhone: Settings > General Settings > About and scroll down to see the IMEI number.
IMEI iPhone
Check IMEI and Carrier of the device on iPhone settings
  • For Android device: Settings > About phone > IMEI
IMEI Android
Check IMEI of the device on Android settings

STEP 2: After getting the IMEI number, we begin to check the status of the device for Docomo, AU, Softbank networks as follows:

a. Visit the summary of network operators via this URL:

b. Fill your IMEI number into the 「IMEI/MEID入力」box (15 digits).

c. After filling up the IMEI number, check the boxes below corresponding to the carriers you want to check in the “チェック対象” section:

KDDI = AU network
SBM系 = belongs to Softbank network
Docomo = Docomo network
Mineo = Mineo network (aggregated operator)
UQモバイル= sub-network of AU

d. Click the ‟チェックする” button to conduct the test. And the test result will appear as below with one of these icons: 〇、△ 、✕、―

: This device is currently in normal use without blocking. Nor the phone is reported as lost or breach of contract.

: The device is not blocked, can still be used normally but is in the process of installment payment or has limited usage. If you later breach of contract (not completing installment amount of the phone for continuous months) or your device is reported as lost, it will be locked and turned into the state [x] as below.

: The device is in a state of being blocked, restricted, or banned due to blacklisting. That means the device will not be able to use the sim of the carrier that released the device as well as any other sim due to breach of contract or loss.

: IMEI number is unable to confirm

  • It is possible to enter the wrong IMEI number or the device is an international version without a contract of use with any carrier in Japan. For this result, if your device is a genuine purchase at a chain store with a warranty, it is completely safe to use JP SMART SIM.
  • It is also possible that your device is a second-hand Japanese phone that has been cracked to make it to an international version, or using jailbreak. In this case, your device will not be able to use JP Smart Sim. Please be careful!

For example IMEI number is「355691074560399」

Insert your phone’s IMEI number into the chatbox

Here comes the result:

According to the test results above, this iPhone’s carrier is AU and the device works normally.

There is an important thing that many customers don’t notice is that JP Smart SIM is only compatible with:

◆ International version Android or iOS devices (including those bought in your home country, not locked to any specific provider)

◆ Unlocked Android or iOS devices

◆ Docomo locked devices.

If your device is AU/SoftBank SIM locked, unfortunately, it will not work with JP Smart SIM. You can bring your locked device to the Carrier shop and ask them to unlock it for you. However, with the test result above, the AU sim-locked device must be upgraded to the international version in order to use JP Smart SIM.

From February 2019, DOCOMO allows users to unlock their phones without authenticating to be the original contractor. From September 2019, AU and Softbank also allow all user to unlock device and upgrade it to international SIM version.

If you are the original contractor, you can unlock your smartphone for free via the homepage of your network carrier. And if you are not the original contractor but the device is eligible, it can be unlocked. But you have to go to the Carrier’s shop and will be charged!

Conditions to unlock network for free:

  1. Unlockable phones: Only Japanese phones sold since May 2015 can be unlocked.
  2. Being in the unlockable period.
    1. Fully paid device: Can unlock anytime
    2. Installment paid device: Can unlock after 100 days of contracting or fully pay the remaining installment amount for the device.
    3. Contracted device but have canceled the contract with the network carrier:
      1. For AU, Softbank device: it can only be unlocked within 100 days from the date of cancellation. After 100 days, you can not unlock it yourself and have to go to the Carrier store to carry out the unlocking procedure and will be charged.
      2. For Docomo device: from April 2, 2019, it will no longer require an identity for the contracted phone. So even when you canceled the contract after 100 days, you can still unlock it yourself if it’s not locked by the network operator.
  3. Not being blocked by network operators: Phones that are lost or have not paid for the installments, used fake documents to register, etc… will be blocked by the network operators. So they cannot use the sim of that network anymore.

If your mobile device meets one of the above conditions (except for the blocked type) then you can completely log into the operator’s homepage to unlock your device, completely free of charge. If you are not fluent in Japanese and not sure which category needed to go on the Carrier official home page, just simply go to Google to search for the keyword: SIMロック解除 + carrier’s name (AU / Docomo / Softbank / Y ! mobile / UQ) to get a direct link accessing to unlock procedure.

Access link for unlocking AU mobile
Access link for unlocking Softbank mobile
Access link for unlocking Docomo mobile


So, JP Smart SIM has finished to instruct you on how to check the sim-lock status of your phone in Japan. Please note that this result is only valid at the time of testing, so in the future, it may be different if the device has unpaid payments or stolen, etc. So if you want to buy a cheap smartphone to use in Japan, it is best to buy at the trustworthy chain electronics stores such as BIG CAMERA, YODOBASHI, or SOFT MAP for your sake.

If you have any questions, please leave a comment below.