Input Tests — Keyboard, Mouse & Touchscreen
By Jayadeep · Last updated: August 2026 · How we test
Five browser tests covering the three things you touch all day — keyboard, mouse and touchscreen — including the double-click fault that makes a mouse feel possessed.
Input hardware wears out mechanically, and it does so on a schedule you can almost predict from usage. A mouse button is a physical switch rated for a finite number of clicks; a keyboard switch has a similar rating; a touchscreen digitiser degrades where your thumb rests. The tests here surface that wear early, while it is still an annoyance rather than a work stoppage, and they distinguish a genuinely failing component from a software or driver problem that looks identical to the user.
The most misdiagnosed fault in this category is mouse double-clicking. The symptom is that a single deliberate click registers as two, so files open when you meant to select them and text selects when you meant to place the cursor. It feels like a software problem — people reinstall drivers and change system double-click speed for weeks — but it is almost always mechanical. The metal contact inside the switch has worn to the point where it bounces on contact, closing and reopening in a couple of milliseconds. Firmware debouncing hides this for a while and then stops being able to. The double-click test times the interval between registered clicks, so a fault that your hand cannot feel becomes visible as a number.
Keyboards fail differently. Individual switches die, producing a key that never registers; contacts get dirty, producing a key that registers twice from one press; and cheaper membrane keyboards hit rollover limits, where pressing several keys at once causes some to be silently dropped. That last one is not a fault at all — it is a design limitation called ghosting, and it matters mostly for gaming and fast typing. The keyboard test shows every keypress as it arrives, along with the key code the browser receives, which also settles the separate question of whether your layout is mapped the way you think it is.
Touchscreens have their own failure signature: a region that stops responding while the rest of the panel works normally. Because the dead zone is usually a band rather than a point, and because you unconsciously adapt by tapping slightly off-target, it can take a long time to notice. Dragging continuously across the whole surface makes the gap obvious immediately. Ghost touches — inputs registering with nothing touching the screen — are the inverse fault, and are frequently caused by a poor-quality charger injecting electrical noise rather than by the digitiser itself.
Every input test
Which test do I need?
Most input faults are mechanical wear, but two common ones are not faults at all — ghosting and layout mismatches. Match your symptom below before you replace anything.
| What you are seeing | Start here | Why this one |
|---|
| One click opens things twice | Double-Click Test | A worn switch bouncing on contact. The test times the gap between registered clicks so you can prove it rather than guess. |
| A key does nothing, or types twice | Keyboard Test | Every keypress appears as it arrives. A key that never shows is a dead switch; one that shows twice from a single press has a dirty or worn contact. |
| My mouse cursor jumps or stutters | Mouse & CPS Test | Checks buttons, scroll wheel and movement tracking together, which separates a sensor problem from a button problem. |
| Some keys stop working when I hold several at once | Keyboard Test | That is ghosting — a rollover limit rather than a fault. Press the combination and watch which keys are silently dropped. |
| Part of my touchscreen ignores me | Touchscreen Test | Drag slowly across the whole panel. Any gap in the trace is a dead zone in the digitiser. |
| I want to measure my click speed | CPS Test | Clicks per second over 1, 5, 10 and 30-second windows — a benchmark rather than a fault test. |
Troubleshooting guides
Step-by-step fixes for keyboard, mouse and touchscreen problems, including the ones that turn out to be settings rather than hardware.
Frequently Asked Questions
Why does my mouse double-click when I click once?
The micro-switch inside the button has worn. As the metal contact ages it starts to bounce when pressed, closing and reopening within a few milliseconds, and the computer correctly reads that as two clicks. Controller firmware masks the effect for a while by ignoring impossibly fast repeats, but once the bouncing worsens it becomes visible. It is a mechanical failure and it gets worse, not better.
Can a double-clicking mouse be repaired?
Yes, though it depends on your tolerance for disassembly. The switch can be replaced by soldering in a new one, and on some switches the internal contact leaf can be cleaned or re-tensioned to buy time. Neither is a permanent fix if the button has simply reached the end of its rated life. Replacing the switch with a higher-rated or optical type is the durable answer.
What is keyboard ghosting?
Ghosting is when pressing several keys simultaneously causes some of them not to register, because the keyboard's wiring matrix cannot distinguish every combination. It is a cost-driven design limitation of most membrane keyboards rather than a defect. Keyboards advertising N-key rollover wire each key so that any combination registers correctly.
Why does one key type the wrong character?
That is usually a layout mismatch rather than hardware. If your operating system is set to a different keyboard layout than the physical keyboard you own, the key codes are correct but the characters mapped to them are not. The keyboard test shows the raw key code the browser receives, which distinguishes the two cases immediately.
What causes ghost touches on a touchscreen?
The most common cause is electrical noise from a low-quality or failing charger, which is why the problem often appears only while charging — unplug and see whether it stops. Other causes include a damaged digitiser, moisture under the glass, and screen protectors that trap contamination against the panel.
Is a high clicks-per-second score meaningful?
Only as a benchmark against yourself or others, not as a measure of hardware health. CPS reflects technique and the speed of your hand far more than the mouse. If your goal is to find a hardware fault, the double-click test is the relevant one.
Other test categories
Audio tests · Screen tests · Controller tests · Performance tests · Camera tests
Keystrokes and clicks are handled entirely inside the page so the tests can display them. Nothing is logged, stored or sent — this is not a keylogger and there is no server to receive anything. How we validate these tests.