How to Check a Used Samsung Galaxy Before You Buy It (2026)

Samsung Galaxy phones hold their value well, which makes them one of the most traded used phones in the world — and one of the most tampered with. Swapped screens, blacklisted IMEIs, phones still tied to a Google account and US carrier models sold as “international” are everyday problems.

The good news is that Samsung gives you more built-in diagnostic tools than almost any other brand. With a few dialer codes and two minutes in Settings, you can test the hardware and confirm the phone’s identity before any money changes hands.

Step 1: Read the IMEI and model number

Open the Phone app and dial *#06#. You’ll see the IMEI (two on dual-SIM models) and usually the serial number. Then compare with Settings › About phone › Status information › IMEI information. The numbers must match each other and the label on the box.

Now look at Settings › About phone for the model number, such as SM-S928B. The letters after the digits tell you which market the phone was built for:

A Samsung Info report confirms the model, region, production date and warranty status from the IMEI, so you can catch a “Galaxy S24 Ultra” that’s really a cheaper model or a different region. For a second opinion use Samsung Info S2. Our Samsung IMEI and warranty guide explains every field.

Step 2: Check blacklist and carrier lock

Run a GSMA blacklist check to make sure the phone hasn’t been reported lost or stolen. For US models (U suffix) add the USA blacklist / barred check, which also flags phones barred for unpaid balances.

Then confirm the network status. Insert your own SIM and make a call — if you see “SIM not supported” or “Network locked”, the phone is carrier-locked. A carrier + SIM-lock check tells you which carrier it belongs to before you meet.

Step 3: Make sure no account lock is left

Samsung phones can carry two separate account locks after a reset:

• Google Factory Reset Protection (FRP): if a Google account was on the phone when it was reset, setup asks for that account.
• Samsung Reactivation Lock: tied to the Samsung account and the Find My Mobile / SmartThings Find feature.

Ask the seller to open Settings › Accounts and backup › Manage accounts and remove every Google and Samsung account, then do Settings › General management › Reset › Factory data reset in front of you. When the phone restarts at the welcome screen, you should be able to set it up with your own account without being asked for anyone else’s. Read how to factory reset a phone properly for the full process.

Step 4: Look for Knox Guard and finance locks

Phones sold on installment plans, by carriers or by companies can be enrolled in Knox Guard or a device-management system. If payments stop, the phone can be locked remotely with a full-screen message — sometimes weeks after you bought it.

Signs to look for: a “Device managed by your organization” or payment reminder notification, an unfamiliar admin app under Settings › Security and privacy › Other security settings › Device admin apps, or a lock screen message mentioning a lender. If you see any of these, don’t buy unless the seller shows proof the device is paid off and released.

Step 5: Test the hardware with Samsung secret codes

Samsung’s built-in test codes let you check the screen, touch, sensors and speakers without installing anything. Open the Phone app and type the code — most run instantly without pressing call:

*#06#
*#0*#
*#1234#
*#0228#
*#12580*369#

What each code does

• *#06# — shows the IMEI(s) and serial number.
• *#0*# — opens the hardware test menu. Tap Red, Green, Blue, Black and White to inspect the display for dead pixels, tint and burn-in. Tap Touch and draw over every square to find dead zones. Receiver, Speaker, Vibration, Sensor and Mega cam / Front cam test the rest.
• *#1234# — shows the firmware versions (AP, CP and CSC). The CSC hints at the region or carrier the phone was set up for.
• *#0228# — battery status screen with voltage and level information on many models.
• *#12580*369# — main software and hardware version summary.

Some US carrier models and newer One UI versions disable certain codes. That alone isn’t suspicious — just use the Samsung Members app instead (below). Avoid any code you don’t recognize: some service codes can reset the phone or change network settings.

Step 6: Run Samsung’s own diagnostics

Open the Samsung Members app, go to Support › Phone diagnostics and tap “Test all”. It checks the battery, sensors, buttons, cameras, Wi-Fi, Bluetooth, NFC, mobile network and charging, and gives a clear pass/fail for each. On recent One UI versions the same tool is also under Settings › Battery and device care › Diagnostics.

While you’re there:

• Battery: the diagnostics battery result reads “Normal”, “Weak” or similar. Newer models also show battery information in Settings › Battery.
• Screen: on AMOLED panels, look at a plain gray image at medium brightness. Faint shapes of the keyboard or status bar mean burn-in.
• Fingerprint and face unlock: register a fingerprint, test it, then delete it.
• S Pen (Ultra and Note models): confirm it docks, charges and writes across the whole screen.
• Samsung Pay / Wallet and Secure Folder: if these refuse to work, the phone may have been rooted, which permanently trips the Knox security flag.

Step 7: Final checks before you pay

1. The IMEI from *#06# passed blacklist and Samsung Info checks.
2. All Google and Samsung accounts are removed and the phone was reset in front of you.
3. No Knox Guard, finance or “managed device” messages.
4. Your SIM works and makes calls with mobile data.
5. Screen, touch, cameras, speakers and charging all passed.
6. You have a receipt or written note with the IMEI and the seller’s details.

Run any remaining report right here:

For the bigger picture, including how to avoid payment tricks at the meeting, read our safe marketplace buying checklist or the full Samsung IMEI check page.