---
title: "Keyboard Tester: Keys, Rollover & Chatter | Flicker Button"
description: "Test every key on an ANSI, ISO or Mac keyboard: see key and code values, how many keys register at once, and keys that chatter or double-type."
url: https://flickerbutton.click/keyboard-tester/
---

03 Input test

# Keyboard tester

Press every key and watch it light up. Hold several at once to find your keyboard's rollover limit, and catch keys that type twice for one press.

## How to use it

Click the keyboard, then press each key in turn: it flashes while held and stays marked once tested. To check rollover, hold keys you use together, such as W, A, D, Shift and Space, and watch "Held now". Chatter is a single press that registers twice; the tester flags a second press of the same key that arrives sooner than the threshold. Press `Esc` twice to leave the test area.

## ISO, Mac and other layouts

The `code` value names the key's physical position, using US key names whatever language your system types in; `key` is what it types. ISO boards add a key beside the left Shift (`IntlBackslash`) and have a tall Enter with the # key beside it. On a Mac, Command is `MetaLeft`/`MetaRight` and Option is Alt. macOS does not send key releases while Command is held, so the tester lets go of those keys when Command comes up. Japanese and Brazilian keys appear under "Keys not on this layout".

## Keys a page cannot see

Your system or browser keeps some keys to itself: the Fn key, many media keys, and shortcuts such as `Ctrl`+`W` or `Alt`+`Tab`. On Windows, Print Screen usually only sends its release. A key that never lights up in any browser points to the keyboard.

## Questions

**What is key rollover?**

How many keys a keyboard can register at the same time. Many basic keyboards miss some combinations of three or more keys; gaming keyboards often handle six or all of them.

**Which chatter threshold should I use?**

Start at 50 ms. Fast typists rarely hit the same key twice within 50 ms on purpose, while a bouncing switch usually repeats within a few milliseconds. Lower it if fast double letters get flagged.

**Is what I type recorded?**

No. Key events are shown on this page only and are gone when you press Reset or leave. Nothing is sent anywhere.