What are ESN Checks, and How Do You Read the Report?

Navigating potential risks when purchasing old cell phones can be difficult. Verifying the device's Electronic Serial Number (ESN) is important in ensuring its reliability. 

An ESN check is similar to a background check for your phone, disclosing its history and highlighting potential red flags. This article will take you through ESN checks, explaining what they are, how to interpret them, and how to check the ESN on different phone carriers.

What does an ESN check entail?

An ESN check confirms the Electronic Serial Number (ESN) linked with a particular mobile phone. This unique 32-bit identification serves as a fingerprint for your phone and is permanently tied to it by the manufacturer. Carriers operating CDMA (Code Division Multiple Access) networks, such as Verizon and Sprint, use ESNs primarily for identification and activation.

An ESN check retrieves data about the phone's history with the carrier. This information could include:

  • Activation status: This indicates if the phone is now active on the carrier's network.
  • Blacklist status: Indicates whether the phone has been reported as lost, stolen, or involved in fraudulent behavior, rendering it unusable on the carrier network.
  • Repair history: The carrier may provide information on any repairs or replacements made to the phone.
  • Contract status: In some circumstances, the ESN check may suggest that the phone is still contracted with the carrier.

What is an IMEI?

In contrast to the dominance of ESNs in CDMA networks, phones connected to GSM networks (e.g., AT&T and T-Mobile) depend on an alternative identification system known as the International Mobile Equipment Identity (IMEI). 

This distinct 15-digit code operates analogously to that of an ESN, serving as an immutable identifier for your device. The IMEI, similar to the ESN, is imprinted indelibly onto the phone during production and serves as an essential identifier for network providers.

Comparable in functionality to an ESN check is an IMEI check. It thoroughly examines the phone's GSM network history and uncovers valuable information. This may encompass the phone's activation status, which signifies its operational state on the carrier's network. 

More significantly, an IMEI check can disclose the blacklist status of a phone. If the phone has been reported lost, stolen, or implicated in fraudulent activities, it will be placed on a blacklist, rendering it functionally inaccessible on the GSM network. In addition, an IMEI check may yield information regarding any replacements or repairs the carrier may have made to the device. 

Occasionally, the review may also specify whether the phone is still covered by its carrier contract. An IMEI check provides significant knowledge of the phone's history, enabling you to formulate well-informed judgments regarding its current state and prospects.

How to Check an IMEI Number?

Most smartphones have their IMEI number readily accessible. Here's how to find it:

  • *Dial #06#: This universal code displays your phone's IMEI number on the screen.
  • Check the phone's settings: Navigate to your phone's Settings app and look for options like "About Phone" or "Status." The IMEI number should be listed there.
  • Look beneath the battery (applicable to some older phones): The IMEI number might be printed on a sticker located beneath the phone's removable battery.

Once you have the IMEI number, you can utilize various free online services or carrier-specific tools to perform an IMEI check.

What is a Clean ESN?

A clean ESN indicates that the phone is not blacklisted and has no reported history of loss, theft, or fraudulent activity. It should also be fully functional on the carrier's network without outstanding contracts or restrictions.

What Makes a Phone Have a Bad ESN?

Several factors can contribute to a bad ESN:

  • Reported lost or stolen: If a phone is reported lost or stolen, the carrier will blacklist its ESN, rendering it unusable on their network.
  • Unpaid bills: In some cases, carriers might blacklist a phone if the associated account has outstanding bills.
  • Manufacturer defect: A phone deemed faulty by the manufacturer might be blacklisted and assigned a bad ESN.

How do you check the ESN on your phone?

Here's how to check the ESN on your phone, depending on your carrier:

  • Verizon and Sprint: Dial *228 from your phone and press "send." You'll receive a text message with details about your phone's ESN and activation status.
  • Contact your carrier: You can also contact your carrier's customer service department and provide them with your phone number. They can verify your ESN status.

Diagnostics Software for ESN Checks

Some third-party diagnostic software applications claim to offer ESN checks. However, it's essential to exercise caution when using such apps. Not all apps are reliable, and some might even contain malware. It's generally recommended to rely on official carrier methods or reputable online IMEI/ESN check services.


How to check if an AT&T phone has a clean ESN?

AT&T primarily utilizes IMEIs for phone identification. You can check the IMEI number on your phone and use a free online IMEI check service to verify its status.

How to check if a Verizon phone has a clean ESN?

Verizon uses ESNs. You can dial *228 from your phone to retrieve your ESN and activation status. Alternatively, you can contact Verizon's customer service and provide them with your phone number for verification.

How to check if a Sprint phone has a clean ESN?

Similar to Verizon, Sprint utilizes ESNs. Dial *228 on your Sprint phone for a text message with your ESN and activation details. You can also reach out to Sprint's customer service department for verification.

How to check if a T-Mobile phone has a clean ESN?

T-Mobile primarily uses IMEIs. Locate your phone's IMEI number and utilize a reputable online IMEI check service to verify its status.


An ESN check is a valuable tool when considering a used phone purchase or verifying the status of your device. You can make informed decisions by understanding what an ESN check reveals and how to interpret the results. Remember, a clean ESN signifies a phone that is not blacklisted, functional on the carrier's network, and free of any outstanding obligations.

Here are some additional tips for a safe and successful used phone purchase:

  • Always perform an ESN or IMEI check before finalizing the purchase.
  • Meet the seller in a public location and avoid money transfer transactions.
  • Inspect the phone thoroughly for any physical damage or signs of malfunction.
  • Consider purchasing from a reputable source or trusted seller.
  • Back up your data regularly, regardless of whether you're using a new or used phone.

By following these guidelines and utilizing ESN checks effectively, you can navigate the world of used cell phones with greater confidence and peace of mind.