iPhone test - full diagnostic check

Safari's limits, stated up front

An iPhone test in a browser is more limited than the same test on Android, and pretending otherwise would produce a confident, wrong report. The differences that matter:

• Vibration cannot be triggered at all. Safari has never implemented the Vibration API, and Chrome and Firefox on iOS are Safari underneath, so no browser on any iPhone can buzz the motor. That is recorded as not supported, not as a failure — the motor may be perfectly good.
• Motion sensors need permission. iOS asks before a page may read the accelerometer, and the prompt only appears after you tap.
• Battery health is not readable. No browser reports wear. Take the figure from Settings > Battery > Battery Health and enter it; it is labelled as entered by you.

Activation Lock is the one that costs the most

An iPhone still signed in to somebody else's Apple ID cannot be set up and is worth almost nothing. No web page can check this. Ask the seller to erase the device in front of you and take it through to the Hello screen and past setup — that is the only proof.

What Safari does check well

Touchscreen coverage and multi-touch, the display through full-screen colour fields, both cameras, the microphone with a live level, the speakers, orientation and rotation, and connectivity. That is most of what goes wrong with a used iPhone.

Related tools

Dead pixel test, touchscreen test, microphone test.