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How to check a used iPhone with 3uTools and Soi Máy

Updated September 27, 2026

Repair techs often say "plug it into 3uTools" before you buy a used iPhone. 3uTools reads things a browser can't: whether the parts are original and how many times the battery has been charged. What it can't tell you is whether the speaker crackles, a corner of the screen ignores touch, or Face ID actually works. This guide shows how to use both tools together in about 15 minutes: 3uTools looks inside, Soi Máy tests what you can see and hear, and you end up with a report you can share.

Tip: 3uTools needs a computer and a cable. If you're meeting a seller without a laptop, run the Soi Máy part in Safari first, then arrange to plug the phone into 3uTools somewhere you trust.

1. Check this before 3uTools

No tool can unlock an iPhone with Activation Lock, so check it first, on the phone:

  • Settings: the top line must be empty and Find My iPhone must be off.
  • Best of all, have the seller erase the phone in front of you and set it up yourself.

The full steps are in how to check a used iPhone. If the phone is still linked to someone's Apple ID, stop there; there's no point plugging it in.

2. Set up 3uTools

  • A Windows or Mac computer, with 3uTools downloaded from the official site, 3u.com. Don't rely on an unknown copy already installed on the seller's computer.
  • A good cable (Lightning or USB-C, depending on the model).
  • Connect the iPhone, unlock it, tap Trust and enter the passcode. Until you tap Trust, 3uTools can't read anything.

Viewing the report only reads information. Don't press the buttons for upgrading or downgrading iOS, jailbreaking or "cleaning up" on someone else's phone.

3. Read the verification report

Once connected, the 3uTools main screen shows the device details. Open the verification report (the button name may differ slightly between versions). It compares the serial number of each part read from the phone with the factory record:

  • Parts that match show as Normal (usually in green).
  • The ones that most often differ: screen, battery, rear camera, Face ID or Touch ID. A mismatch means the part may have been replaced.
  • Also check the production date, sales region and jailbreak status.

Don't treat the report as final. On newer models or iOS versions some lines can show as unknown even on an untouched phone, and a skilled repairer can move serial numbers onto new parts. Cross-check on the iPhone itself: since iOS 15.2, go to Settings › General › About › Parts and Service History. When both say a part was replaced, you can be fairly sure it was.

4. Battery: charge cycles and real capacity

In the battery details in 3uTools, look at two numbers:

  • Charge cycles: the higher, the older the battery. A phone used for one or two years usually has a few hundred.
  • Actual capacity versus design capacity: compare it with Settings › Battery › Battery Health on the iPhone. The two should be close. If they're far apart, ask whether the battery was replaced.

To see how quickly the battery drains in real use, add the Soi Máy battery test:

Battery and charging port testSee the battery level, catch a loose charging port by plugging in and out, and watch how fast it drains. Plus where to read battery health.

5. What 3uTools can't see: test it with Soi Máy

Unplug the cable, open soimay.com in Safari on that iPhone and go through the tests. A screen marked "Normal" in 3uTools can still have dead pixels or a yellow tint.

  • Screen: step through solid colours to spot dead pixels, tints and blotches.
Dead pixel, backlight bleed and burn-in testFind dead or stuck pixels, backlight bleed, burn-in and lines on a phone or laptop screen. Eight full-screen colours, free, no app to install.
  • Touch: fill the grid to find dead or jumpy areas.
Touch screen test: dead zones and ghost touchesSwipe to fill a grid of cells and spot dead touch zones or ghost touches on a phone or tablet. Runs full screen, free.
  • Speakers and microphones: the speaker test plays the top and bottom speakers separately; the mic test records and plays back.
  • Cameras: the camera test opens each camera so you can look for haze, dust or streaks.
  • Face ID or Touch ID: an original part that doesn't recognise you is still a fault. Try it with the biometric test.
  • Things you check by eye: buttons, signal, the body, the water indicator. The checklist walks through each one.

6. Two reports, one decision

  • 3uTools normal and Soi Máy all passed: a good phone; the price comes down to cosmetics and battery.
  • 3uTools shows replaced parts but Soi Máy passes: it works, but it should cost less than an untouched phone. Ask where the repair was done and whether any warranty is left.
  • Soi Máy shows a fault: it's a real fault, whatever 3uTools says.

When you're done

Take a screenshot of the 3uTools report, then save the Soi Máy results as a PDF or a link and QR code on the Results page. A seller can send both to a buyer far away, and a buyer can keep them to compare against if something goes wrong during the warranty.

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