I Built a Free Keyboard Tester in the Browser — Here's Exactly How It Works (and How to Use It)

A free keyboard tester has been created, which can be used directly in a web browser. This tool has been built by the author of Key & Pixel, a site that offers free browser tools. The keyboard tester is designed to detect common keyboard issues such as double-registering, stuck keys, and rollover limits.

To use the tool, you first need to select the type of keyboard you have (full, TKL, 75%, 65%, 60%, laptop, ANSI, or ISO) and the platform (Windows or Mac). Then, open the tester, click anywhere on the page to focus it, and press each key row by row. Each key will light up when pressed and stay shaded after release, allowing you to track which keys you have already tested.

The tester counts single presses as well as double-presses, which is a common sign of a failing keyboard. If a key is held for more than 3 seconds without you pressing it, it will also be flagged. The tester also measures the auto-repeat and typing accuracy of your keyboard, which can be useful if you suspect an OS setting rather than hardware issues.

Under the hood, the tester uses keydown and keyup events to monitor the keyboard input. It uses the code property to identify the key, which is layout-independent, and the keyCode and location properties to add additional information. The tester also suppresses the browser's default reaction to certain keys such as Tab, Space, Backspace, and function keys, so pressing these keys only tests the key itself.

Three real-world behaviors were identified that needed explicit handling: Windows AltGr sending an invisible Left Ctrl event, macOS Caps Lock firing two events when switching on and off, and macOS + UK (ISO) keyboards reporting certain keys with each other's codes. These issues were handled so that the tester provides accurate results.

However, it's important to note that the browser-based tester has limitations. It only sees the keys that the OS and browser pass along, so it cannot detect functions reserved by the browser (like Ctrl+W, Ctrl+T, Cmd+Q) or hardware-specific keys such as Fn, Touch ID, and media keys. For such cases, a driver-level tool would be needed. The tester is free, needs no signup, stores no data, and can be accessed at keyandpixel.com/keyboard-tester.