[Warning] What is a network usage restriction? A thorough explanation of how to identify and check for a red-ROM device

When looking for a used smartphone, you might come across terms like "network usage restrictions" and "red ROM."
These are unfamiliar terms, but if you buy one without knowing what they mean, you could end up with a "useless smartphone."

This article explains the mechanism of network usage restrictions on smartphones, how to check them, and checkpoints for purchasing safely, in an easy-to-understand way for beginners.

What are network usage restrictions?

Network usage restrictions are a communication restriction mechanism introduced by mobile carriers (such as Docomo, au, and SoftBank) to prevent "fraudulent use" and "non-payment."

Devices that have been stolen, lost, or have unpaid balances are set to a state where communication and calls are not possible (referred to as "red ROM") at the discretion of the carrier.
This prevents fraudulently obtained smartphones from being misused.

Main reasons for restrictions

• Devices reported as stolen or lost

• Installment payments are outstanding

• Fraudulent acquisition of subscriber information or fraudulent contracts

In other words, network usage restrictions are a security feature implemented by carriers to protect societal safety.

How to identify the restriction status

Network usage restrictions can be checked using the "IMEI (International Mobile Equipment Identity)" assigned to each device.
The IMEI is like a smartphone's "individual identification number" and can be checked using the following steps:

Steps to check IMEI on iPhone

1. Open the "Settings" app

2. Tap "General" → "About"

3. Locate the 15-digit number for "IMEI" or "IMEI1" in the list

By entering the confirmed IMEI into each carrier's inquiry page, you can check the usage restriction status.

In particular, devices marked with "×" (cross) are in a "red ROM" state, meaning communication and calls are completely impossible.
While they can be used in a Wi-Fi environment, they are unsuitable for daily use as a smartphone because they cannot connect to a cellular network even with a SIM inserted.

Differences between "Red ROM," "White ROM," and "Black ROM"

In the used smartphone market, the status of network usage restrictions is referred to by the following terms:

• White ROM: No restrictions (〇) = Safe device with communication capability

• Red ROM: Restricted (×) = Device with no communication capability

• Black ROM: Device suspected of fraudulent acquisition and at risk of becoming a red ROM in the future

Shops that explicitly state "Red ROM warranty included" have a system in place to offer exchanges or refunds if the device unfortunately becomes × after purchase.
When buying a used device, always check for the presence of this warranty.

Once "×", it cannot be unlocked.

If network usage restrictions become "×", it is highly unlikely that carriers will lift the restriction.
This is because the restriction is imposed as a result of detecting contract violations, such as non-payment.
Even if the original contract holder settles the payment later, it is extremely rare for the restriction to be lifted based on the carrier's internal judgment.

Therefore, purchasing with the thought that "it might be lifted later" is very risky.
Once a device becomes a red ROM, it enters a semi-permanently communication-disabled state.

Essential checks before buying a used iPhone

When purchasing a used iPhone, always confirm the following points to avoid problems.

① Check the reliability of the retailer

Major used goods shops and specialized reuse dealers only sell devices that have already passed network usage restriction checks.
On the other hand, in peer-to-peer transactions (flea market apps, auctions, etc.), conditions and warranties are often ambiguous, so caution is necessary.

② Inquire from the carrier's official page using IMEI

Each carrier has a dedicated inquiry site.
Before purchasing, be sure to enter the IMEI and check the status.

• Docomo Official: Network Usage Restriction Check

• au (KDDI) Official: Network Usage Restriction Inquiry

• SoftBank Official: IMEI Confirmation Page

③ Check if a "Red ROM warranty" is available

If the retailer offers a warranty, you can rest assured even if the device status changes from "△" to "×" after purchase.
Always check the warranty details (period, coverage) before purchasing.

Also note the difference between network restrictions and SIM lock

Often confused is "SIM lock."
SIM lock is a setting that prevents the use of SIM cards from carriers other than a specific one, and it is unrelated to the device's payment status.

On the other hand, network usage restriction means that "the device itself is being treated as fraudulent."
Unlocking the SIM lock will not restore communication.
Understanding this difference correctly can prevent problems after purchase.

【Summary】 For used iPhone purchases, always ensure "IMEI check" + "with warranty" for peace of mind.

Network usage restrictions are an important system for safely using smartphones.
However, if you unknowingly purchase a "red ROM" device in the "×" state, you could end up with a "bricked smartphone" that cannot communicate.

Checking the IMEI before purchase and confirming the retailer's warranty details are the best measures to avoid trouble.

【PRODIG offers peace of mind】Used iPhones available with a 6-month red ROM warranty.

PRODIG (Prodig) includes a "6-month red ROM warranty" as standard for all used iPhones and iPads.
In the unlikely event that network usage restrictions become "×" after purchase, we will offer an exchange or full refund within 6 months.

Furthermore, all listed products have been pre-checked by carriers and had their operations confirmed.
To ensure that even first-time used device buyers can choose with confidence, product pages clearly display IMEI information and restriction status.

If you want to buy a used iPhone with peace of mind, please visit the PRODIG official website.

👉 Find used iPhones on the PRODIG official website