The short answer
First clean and dry the screen safely, confirm touch is supported and repeat the affected action slowly in more than one app. Use Touch Screen Test to map delivered contacts and deliberately retest unmarked areas. If unexpected contacts are the symptom, place the device down and use the short Ghost Touch Watch without touching the test area.
A browser can show contact events, not inspect digitizer electronics. A missed grid cell is an area not reached during the run; it does not prove a dead zone. An unexpected event is evidence to compare, not automatic confirmation of ghost touch or a specific repair.
Practical checklist
- Power off for cleaning when recommended and follow the device maker’s guidance.
- Remove moisture, dirt and unsupported gloves; inspect protectors without forcing removal.
- Start coverage and trace slowly across the affected region and neighboring cells.
- Retest missed areas; compare another browser and an operating-system app.
- For unwanted input, run the three-second countdown and ten-second watch without contact.
- Compare safe supported charging conditions and seek manufacturer help for persistent or unsafe symptoms.
Separate missing input from unexpected input
A dead-zone complaint means deliberate contact is not producing the expected response in a region. Ghost-touch complaints usually mean input appears without an intended touch. These are different observations and need different procedures. A broken drag path can also be caused by an app interpreting a gesture, a contact leaving its area or event sampling skipping positions, so begin with a clear repeatable action rather than a repair label.
Write down the symptom without sensitive details: which area, whether it happens in one app or several, whether the device is charging and whether the screen is dry. Do not assume all missed taps are hardware damage or all stray actions are electrical interference. A consistent description lets you compare one condition at a time and gives manufacturer support useful information without sending a raw touch-coordinate trace to analytics.
Map coverage slowly and understand the grid
Touch Screen Test divides its active area into twelve columns and eighteen rows. When a touch pointer position lands inside a cell, that cell receives a mark. Mouse events never complete this touchscreen map, and pen input is noted separately. Begin with slow rows and columns, then deliberately cross corners and the region that concerns you. The browser does not interpolate a line between samples, so a quick swipe may leave gaps even on a working surface.
Finish the run and select Retest missed areas to preserve existing coverage while tracing the unmarked cells again. A marked cell establishes a reported touch somewhere inside that cell, not every point of its physical area. Coverage percentage is a summary of this browser grid, not a digitizer-health score. A gap that disappears during careful retesting has a different evidential value from the same region repeatedly failing across apps.
Why edges and broken drag paths need context
Operating-system navigation gestures may intercept contacts near the edge before a web page receives them. Browser toolbars can also reduce the available area. Optional fullscreen is requested only after your action and can improve coverage, but it does not disable system gestures or expose parts of the panel outside the page. Escape and the exit control remain normal ways out.
If dragging breaks near one boundary, start the same motion well inside the page and compare a native drawing or settings app. Avoid permanently disabling system navigation merely to fill a grid. A drag failure confined to a browser or page layout suggests a different next check from a repeatable region that fails everywhere. This tool cannot decide which OS setting, application handler or hardware layer suppressed a contact.
Multi-touch counts are observations, not certification
The active-contact display counts currently held touch pointer IDs received by the page, and maximum contacts is the largest count seen during the run. Place fingers apart inside the test area, hold them briefly and release fully before another attempt. Closely spaced fingers, a palm, a protector or controller rejection rules may change which contacts are reported.
navigator.maxTouchPoints is shown as a browser-reported capability after you start. It is not a command that forces the device to expose that many contacts. A lower observed maximum may simply mean fewer contacts were made or system gestures intercepted a combination. Some devices reject palms or combine nearby contact shapes. Do not infer that a controller advertised for several contacts is defective from one lower browser count.
Run Ghost Touch Watch without creating the event yourself
The optional watch begins with a three-second countdown so you can set the device down and stop touching it. It then counts touch-down events reported inside the area for approximately ten seconds and shows rough relative positions if events arrive. Do not tap controls or move the device during the watch if you want a useful no-contact comparison. A hidden page cancels observation rather than producing a misleading background result.
An event during the watch could be an unintended real contact, environmental interference or an input problem. No event during ten seconds cannot rule out an intermittent symptom. Repeat under similar conditions and compare with the device’s ordinary interface, without leaving it in an unsafe charging setup. The page does not identify the exact electrical cause or certify whether a display replacement is required.
Moisture, contamination and screen protectors
Many capacitive touchscreens detect changes in an electric field rather than mechanical button pressure. Moisture, grease, unsuitable gloves or a damaged protector can affect the contacts a controller interprets. Inspect the surface under ordinary light and follow the maker’s safe cleaning instructions. Power off and disconnect accessories when recommended, use approved materials and let the surface dry before another deliberate run.
Do not press hard, scrape the panel or apply unapproved solvents because a grid cell is unmarked. If a protector is visibly damaged or incompatible, consult its instructions and the device maker before removal. A result that changes after safe cleaning is useful context but does not prove the protector was the only cause. Liquid exposure, swelling or damaged glass may need professional support instead of repeated testing.
Compare charging conditions cautiously
If unwanted input appears only while charging, compare with a supported known-good charger and cable when safe. Electrical interference is one possible explanation, but a web event alone cannot measure it. Keep the device stable, dry and away from accidental contacts during each comparison. Change only the charging condition so you do not confuse that change with a different app or cleaning step.
Stop using damaged, unusually hot or unsafe accessories; do not experiment with improvised grounding or open electrical equipment. Wireless charging, battery state and accessories may change the environment too, but no universal cause follows from the browser watch. Follow manufacturer support guidance for persistent charging-related symptoms and describe what changed rather than claiming this tool diagnosed a power fault.
Browser, operating-system and hardware follow-up
Restarting the device or updating through supported OS procedures may be appropriate after saving work, especially when the symptom began after a software change. Compare a second supported browser and a native app. If touch fails only in one page, inspect that app’s input behavior before replacing hardware. If a physical region repeatedly fails across independent apps after safe preparation, a device-side problem becomes more plausible but its exact component remains unverified.
Touch Screen Test saves no raw map or coordinates in browser storage and uploads none. Its local observation disappears when you leave or reset. Only consent-controlled start and complete events may be sent. Keep any support note non-sensitive and ask the manufacturer about its recommended diagnostics and warranty process. This is a practical observation method, not an electronic inspection or repair tool.
Frequently asked questions
Does an unmarked cell mean a broken touchscreen?
No. Retest slowly. Fast motion, missed coverage, OS gestures and browser sampling can leave gaps.
Can a mouse substitute for touch?
No. Mouse input does not mark the coverage grid.
Does a ghost-watch event prove hardware ghost touch?
No. It shows a reported touch-down during observation and needs comparison with real contact and environmental conditions.
Should I press or heat the screen to repair it?
No. This guide recommends safe manufacturer-approved cleaning and support, not destructive repair attempts.
Keep the follow-up specific
Explore Full Device Check for a local diagnostic checklist and Video Call Check for meeting preparation. Read methodology for browser limits and privacy for actual data handling. If this guide disagrees with the current tool, contact Testpartout with a correction without private device identifiers or sensitive data.