Know the phone before you pay.
Knowfone tests every part of a used Android phone in about 7 minutes. Then it gives you a straight answer: good to buy, buy only at a lower price, or don't buy.
No account. Your reports stay on your phone.
One of three answers
No scores to decode. Each answer comes with its reasons, the numbers behind them and what Knowfone could not test.
Good to buy
Everything we tested works as it should.
Buy only at a lower price
It works, but some parts have problems that cost money. Now you know what to ask off the price.
Don't buy
We found a serious problem, such as a processor that is not the one this model uses.
The phone proves itself. You watch.
Knowfone does not just read what a phone says about itself, because a modified phone can say anything. Wherever it can, one part tests another and you see, hear or feel the same thing.
Identity
Processor, graphics, memory, screen and storage compared with the model it claims to be. Copies dressed as famous models stand out.
Security
The phone's security chip signs its answer, checked up to Google's root. A tampered system cannot forge it.
Touch screen
Follow a light with one finger across every 7 mm of the glass. Dead strips show up on the map.
Display
Full-screen colour pages for dead pixels, lines and burn-in, and the real refresh rate.
Speakers and mics
The speaker plays a sweep and the microphone hears it. You hear it too.
Cameras
Every lens opens and focuses. The flash fires and the camera sees it.
Battery
Health, charge and how the voltage holds up under load.
Processor and memory
A stress test that checks it stays stable and as fast as this model should be.
Storage
Writes real data and reads it back, to prove the size it claims and find errors.
Sensors
A tilt game, the compass and the sensor that turns the screen off near your ear.
Buttons and port
Volume and power keys, the charging port, and the vibration motor, felt by the motion sensor.
Wireless and SIM
Wi-Fi, Bluetooth, GPS satellites and the SIM.
What no app can check
Knowfone says so in every report, so you know what to check by hand.
Past water damage or repairs inside
Open-and-look work for a repair shop. Knowfone tests whether each part works today.
Stolen, blocked or on a contract
Dial *#06#, compare the IMEI with the box, and check it with your network. Ask the seller to sign out of their Google account in front of you.
Exactly how long it will last
Battery health and a stress test are strong hints, not a promise.
Selling a phone? Show it is good.
Buyers fear clones and phones that die in a month. A seller certificate answers that before they ask.
- Run a full check on your phoneAbout 10 minutes, free.
- Open Seller certificate on the reportOne short ad unlocks it. If no ad is available, it is free.
- Post it with your listingOn Jiji, Facebook or any marketplace. Buyers scan the code to see the report, and can run Knowfone themselves when you meet.
Free, with fair ads
Ads pay for Knowfone. They follow four rules, written into the app's code.
Never during a test
Ads use the processor, network and battery. During a test they would make the numbers less true, so the app blocks them.
Never before your answer
No pop-ups between you and your result.
About the report, not about you
Ads are picked by what is on the screen, like a worn battery, not by who you are.
One optional ad, for sellers
A short ad unlocks the seller certificate. You choose to watch it, and you can skip it.
Questions
Is Knowfone free?
Yes. Every test and every answer is free. Knowfone shows a few ads after your answer, never during a test.
Can it tell if a phone is a clone?
It compares the processor, graphics, memory, screen, storage and cameras with the model the phone claims to be, and asks the security chip for a signed answer checked up to Google's root. A copy that only looks like a famous model usually fails these checks. Knowfone tells you what it measured, for example "not the processor this model uses".
Does it upload my data?
No. There is no account and your reports stay on the phone. A report leaves the phone only when you share it yourself. See the privacy policy.
Which phones does it work on?
Android phones running Android 8.0 or newer, from every brand. Parts a phone does not have are marked "couldn't test", never as broken.
Whose phone do I install it on?
On the phone you are about to buy. Ask the seller to install it, or install it yourself from this page while you hold the phone.
Can it see water damage or tell if a phone is stolen?
No app can. Knowfone says so in every report and lists what to check by hand. Compare the IMEI (dial *#06#) with the box and ask your network operator to check it is not blocked.
Install in three steps
- Tap Download for AndroidThe file knowfone.apk (14 MB) is saved to your phone.
- Open the fileIf Android asks, allow your browser or file manager to install apps.
- If Play Protect warns about an unknown appTap More details, then Install anyway. Knowfone is free, needs no account and asks for each permission only when a test needs it.
Also on APKPure.
No app yet? Test it online.
Ten free tests run in any phone's browser: screen, touch, speakers, microphone, cameras, sensors and the charging port. Or look up the real specs of 24 popular models.