Touch Screen Test: Find Dead Zones and Ghost Touches
That one spot you have to tap twice is worth checking. This touch screen test shows where the browser receives your touches: drag a finger across the grid, then go back over any cells still grey. An empty cell is a place to revisit before calling it a dead zone.
Take your time around the area that bothers you in everyday use. Repeating the same missed spot tells you more than rushing to 100% coverage. The test runs in your browser without an install and belongs to the phone test online suite. The device guidance below covers further checks on Samsung, vivo and Xiaomi phones.
How to test your touch screen
Open the test on the phone you want to check. Drag one finger slowly across the 150-cell grid, then return to any area you missed. Touching now shows active contacts, Max points keeps the highest simultaneous count in this session, and Area covered shows how much of the grid has received input.
Try horizontal strokes, vertical strokes and a pass around the border. Clean and dry the screen first so you can repeat the test under similar conditions. A high coverage number is encouraging for the area you reached, but take another look at any gap that keeps returning.
The test covers the area available to this web page. Rotate the phone or use the fullscreen control to reach more of the display. System controls and browser bars can leave areas outside the test; the manufacturer checks below may help you go further.
Multi-touch and dead zones
A grey cell deserves another pass. Move over it deliberately and see whether the same gap returns. If it does, note the location and compare with the problem you see outside this page. The grid records touch input; it cannot identify the damaged part.
For multi-touch, put several fingers on the screen and watch Max points. That is the highest number of simultaneous contacts seen in this session, not a certified hardware limit. A stable count and continuous paths are more useful to check than a number borrowed from a different phone.
If contacts appear without a finger on the glass, repeat the check with the screen clean and dry. Record what happened before changing conditions. For other checks, return to the phone test online suite.
Android vs iPhone
On Android the browser test is only the first layer. Turn on Developer options → Pointer location and the system draws live crosshairs and exact coordinates over everything, including areas a browser cannot reach — the fastest way to prove an offset. Samsung phones also have Settings → Display → Touch sensitivity, which raises the panel's gain for thick tempered glass. An accelerometer test is worth running too: a drop hard enough to bruise the digitizer often disturbs the sensor stack.
iPhone has no touch-test dialer codes at all. The only codes iOS answers are *#06# for the IMEI and *3001#12345#* for Field Test, and Field Test reports cellular signal — nothing to do with the screen. Test in Safari, then check Settings → Accessibility → Touch in case Touch Accommodations is swallowing taps. If you run a case and a tempered-glass protector together, take both off for one pass: that combination has caused documented unresponsiveness on several iPhone generations.
Secret dialer test codes (Samsung, vivo, Xiaomi)
Every major Android maker ships a hidden service menu that tests the panel at system level — full screen, no browser. Type the code into the stock phone app, because Google Dialer often will not pass it through; most fire on the last character, with no call button.
Samsung
*#0*#— the general hardware test menu. Tap Touch and trace the squares until the X-marked box turns green. The same menu holds the red/green/blue screen tests, sensors, camera, speaker and vibration.*#7353#— Quick Test Menu, a shorter list covering touch, sensors, camera and vibration. Some carrier variants omit it.*#2663#— shows the touch panel (TSP) firmware version and can update it. Use it only if touch is misbehaving; there is no reason to reflash a working panel.
vivo
*#558#— the OQC test menu, vivo's factory hardware check, display and touch included.*#*#2664#*#*— the touchscreen grid test on its own. A generic Android engineering code rather than a vivo exclusive; also reported working on some Xiaomi and MediaTek devices.
Xiaomi, Redmi and POCO
*#*#6484#*#*— the CIT menu, Xiaomi's full hardware test, with a touch-panel test and a run-everything option.*#*#3646633#*#*— MediaTek engineering mode, the fallback on MTK-based models.*#*#0#*#*— LCD colour test, useful when judging a replacement panel.
Read this before you type anything. Some service codes are destructive and run with no confirmation prompt. *2767*3855# is a master reset that wipes internal storage and reflashes firmware; *#*#7780#*#* is a factory data reset; on Samsung, *#272*IMEI# changes the CSC region and wipes the phone doing it. *#*#4636#*#* is safe to open — the phone-information screen, no touch test — but changing the preferred network mode from inside it can break calls, SMS or 5G until you change it back. Test codes only; never a reset code off a list.
Expect misses. Samsung has disabled codes on recent One UI builds, Xiaomi has patched many on HyperOS, vivo on newer Funtouch OS and Origin OS, and carriers block short codes outright — a Connection problem or invalid MMI code message means a blocked code, not a broken phone. The fallback is the maker's diagnostics app: Samsung Members runs a touch screen test under Get help → Diagnostics, alongside the speaker and vibration test. We could not verify a working touch-test code for OPPO, realme, OnePlus, Motorola or Pixel, so we list none.
Touch sampling rate
Touch sampling rate and refresh rate are different numbers. Refresh rate is how often the display redraws — 60, 120 or 144 Hz. Touch sampling rate is how often the digitizer asks the glass where your finger is: typically 120 to 240 Hz, and 480 Hz or more on gaming models. A high sampling rate makes a drag arrive sooner.
No web page can measure it, including this one, and you should distrust any that claims to. Browsers coalesce pointer input and deliver it once per animation frame, so the most touch events a page can count per second is roughly your refresh rate, not your sampling rate.
What the grid does show is consistency. Draw a fast line and look for gaps: a healthy panel leaves a continuous trail, dropped input leaves dashes. Repeatable gaps in the same place point at the panel; gaps everywhere usually mean the phone is throttled or busy, so retest after a restart.
Frequently asked questions
Why does my touch screen have a dead zone down the middle?
A strip that never responds is almost always digitizer damage, not software. The touch layer is a grid of sensing lines, so a crack, a delaminated bond or a pinched flex cable kills whole rows or columns at once — which is why the fault shows up as a band rather than a dot. Run the grid above in both orientations; if the same band stays grey after a restart and with the protector off, the panel needs replacing.
Why does my phone tap by itself, both when charging and unplugged?
Ghost touches that appear on the charger are electrical, and ones that appear off the charger are physical. A cheap or failing charger injects noise through the ground path and the panel reads it as fingers, so swap cable and adapter first. If it also happens unplugged, suspect a dirty or bubbled screen protector, moisture, a swollen battery pressing the panel from behind, or a cracked digitizer.
Why is my touchscreen registering touches in the wrong place?
An offset means the panel's coordinates no longer line up with the display, which is a calibration or firmware problem far more often than a dead panel. It turns up most after a screen replacement or a firmware update. Restart first, then on Samsung check the touch panel firmware with *#2663#. If the offset appears in only one app, it is that app's scaling, not the digitizer.
Touch is not smooth after I applied tempered glass — is it the glass or the screen?
Take the protector off and run the grid again — that settles it in a minute. If the dead or laggy area disappears, the glass is too thick, badly seated or trapping air; a bubble only has to be slightly raised to break contact. If the fault survives on bare glass, it is the digitizer. On Samsung, try Settings, Display, Touch sensitivity before buying another protector.
Touch screen is not working properly after a screen change — bad part or connector?
Test the old screen before you blame the board. Faulty touch is common in third-party replacement panels, so reconnect the original display and run the same grid: if the original works and the new one does not, the replacement part is bad. If both fail in the same way, look at the seating of the display flex and the connector on the board, reseat it, and retest.
How many fingers does multi-touch support on my phone?
Most modern phones handle five to ten simultaneous points, and ten is the usual ceiling; some tablets go higher. What the browser reports can be lower than the panel's real capability, because the operating system caps what it passes to a web page — five on an iPhone is normal. Press as many fingers down as will fit and read Max points; consistency matters more than the number itself.
Why does *#0*# say "Connection problem or invalid MMI code"?
The code is blocked, not broken. Samsung has disabled or restricted several service codes on newer One UI builds, carriers block short codes on their network, and Auto Blocker can stop one running. Make sure you are using the stock Samsung phone app rather than Google Dialer, and try with Wi-Fi Calling off and a cellular signal present. If it still fails, use Samsung Members, Get help, Diagnostics instead.