Keyboard polling rate describes how often your keyboard reports its state to the computer, expressed in hertz (Hz). A keyboard with a 125 Hz polling rate sends an update roughly every 8 milliseconds, while a 1000 Hz keyboard reports about once per millisecond. The higher the rate, the fresher the input data the host receives, which is why gamers and fast typists notice a smoother feel on faster-polling boards. Polling rate is set by the keyboard's firmware and USB reporting interval; the host has no control over it, so the only way to know what you are actually getting is to test the keyboard itself. A real hertz measurement needs precise timing across many presses, but the practical question most users have is far simpler: are any of my key presses being silently dropped, doubled, or arriving late? That is exactly what the symptoms of polling rate issues, rollover limits, and ghosting look like in everyday use, and it is what a hands-on key-by-key test surfaces immediately. The free Keyboard Tester runs entirely in your browser and shows the result of every press on an on-screen layout, so you can confirm in one pass whether every key and every chord on your board is reaching the host.
What keyboard polling rate means
Polling rate is the frequency at which the keyboard reports its current key state to the USB host. The firmware inside the keyboard wakes up on a fixed interval, scans the switch matrix, and sends an HID report listing every key that is currently pressed. The host application then reads that report on its own loop. A 125 Hz keyboard updates about every 8 ms, a 500 Hz board every 2 ms, and a 1000 Hz board every 1 ms. Because the device drives the timing, the host has no way to ask for a faster update, and a misbehaving firmware can produce visible gaps even on a keyboard that is rated for high polling.
The user-visible symptoms of a polling rate problem are not raw timing numbers. They show up as missing characters during rapid typing, lost inputs inside a key chord, or commands that simply do not arrive in the middle of a fast sequence. Those are also exactly the symptoms of rollover limits, ghosting, and dead switches, which is why a practical polling rate test focuses on whether every intended press reaches the application layer rather than on the hertz figure stamped on the box.
What a polling rate test actually reveals
Three failure modes tend to surface during a key sweep, and they all look the same to the user: a press that should have happened did not. A hands-on test separates them.
- Dropped inputs: A key press that the keyboard simply never reports, leaving a missing letter or command inside a burst of typing or a combo.
- Ghosting: Pressing several keys at once, only some of them appear on the host, while the others vanish silently even though your fingers are clearly holding them down.
- Chattering or stuck keys: A single tap registers as multiple events, or a key stays logically pressed after you have released it, both of which point to switch problems rather than rate problems but show up in the same kind of test.
A key-by-key test that marks every registered press lets you map the failing keys and the failing combinations at a glance. If a single key never lights up, the issue is that key, not the rate. If a chord of three or four keys causes one of them to vanish while you are still holding it, you are looking at a rollover or ghosting limit in the keyboard's matrix.
How to test keyboard polling rate using Keyboard Tester
The Keyboard Tester is a free browser tool that listens for keyboard events and lights up the matching key on an on-screen QWERTY layout. Held keys glow while you hold them, and every key you press stays permanently marked as tested, so a full sweep of the keyboard leaves you with a clear visual map of what works and what does not.
- Click or tab into the on-screen keyboard so it becomes active and starts capturing your key presses.
- Press each physical key on your keyboard one at a time and watch the matching on-screen key light up and stay marked as tested.
- Read the last-key panel to check the key, code, and keyCode values reported for the key you just pressed.
- Hold several keys at once to test rollover and ghosting. Watch which on-screen keys stay lit and which ones go dark while you continue holding them; any key that disappears is being silently dropped by the keyboard.
- Look for any on-screen keys that never light up after you have pressed them. Those are likely dead or failing keys.
- Click Reset to clear all tested marks and the last-key readout when you want to run a fresh test pass, for example after cleaning under a troublesome key.
The whole pass takes a few minutes for a full-size board and produces a visual record of every key the browser actually saw, which is exactly the kind of evidence you need when you are troubleshooting why a particular letter keeps disappearing or why a chord does not register during gameplay.
Reading the key, code, and keyCode values
Every time you press a key, the Keyboard Tester shows three values for that event. They all come from the same browser KeyboardEvent but serve different purposes.
| Field | What it represents | Stability |
|---|---|---|
| key | The character or named key the press produces, such as a, Enter, or ArrowUp | Changes with language layout and modifiers (Shift, Caps Lock) |
| code | The fixed physical position of the key on the board, such as KeyA, Space, or ArrowUp | Stays the same regardless of layout |
| keyCode | An older numeric identifier kept for compatibility with software and games | Layout-independent but legacy |
Because the code value follows the physical key, it is the right field to read when you want to check that the browser is receiving the event for the key you actually pressed. If you press the physical A position and the readout shows KeyA, the press arrived correctly. If the readout shows a different letter instead, the issue is either your layout or a remap layer rather than a missing event. The keyCode field is most useful when you are testing keys that some games still bind by number, so you can confirm what number the browser reports before you remap in software.
Spotting rollover, ghosting, and dead keys
Rollover describes how many simultaneous key presses a keyboard can report. Two-key rollover (2KRO) is the bare minimum, full n-key rollover (NKRO) reports every key independently. Most modern USB keyboards handle the WASD movement keys plus a couple of modifiers, but a fast typist or a gamer pressing Shift, Ctrl, and three letter keys at once can easily exceed that.
To test rollover with the Keyboard Tester, hold a modifier like Shift with one hand, then hold two or three letter keys with the other. If every key stays lit on the on-screen layout, that combination is being reported correctly. If one of them fades out while you are still holding it, that key is being dropped by the keyboard's matrix and you have just located the rollover limit. Repeat for the chord patterns you actually use, such as Ctrl plus Shift plus Tab, or the bottom-row modifiers used by games.
Dead keys show up at the end of a full pass. Press every key once and the on-screen layout now shows a lit key for each registered press. Any dark key is either physically disconnected, dirty under the cap, intercepted by an OS shortcut, or held by a stuck switch. The Keyboard Tester cannot tell you which of those is true, but it gives you an unambiguous list to investigate, including the exact code and keyCode values for each working key so you have a reference to compare the dead ones against.
Browser limits and what to do next
No browser tool can measure raw USB polling in hertz the way dedicated firmware tools can. What the Keyboard Tester can do is tell you whether the events your keyboard intends to send are arriving at the application layer, which is the part that affects typing and gameplay. A few keys are also handled by the operating system or hardware before the browser sees them, including some laptop Fn combinations, media keys, and certain lock keys, so those may not register in the tool even when the hardware is fine. If a key stays dark, first confirm the on-screen keyboard is focused; if it still does not light up, the key is likely physically dead, dirty, or intercepted before the browser receives the press.
Everything happens locally in your browser. The page listens for key events and never records, stores, or transmits them, so it is safe to run on any machine even when sensitive text would normally be a concern. When you are done, click Reset to clear the marks and start a fresh pass after cleaning under a key, switching to a different layout, or remapping modifiers in software.