- A key stays grey. Is it broken?
- Not necessarily. Try it in another program first: if nothing registers there either, the switch or the cable is the likely cause. Media keys and vendor keys often send nothing a browser can see, so those staying grey means little.
- Why does the letter shown not match the cap I pressed?
- Because the operating system decides which character a physical key produces. The test reports the position, so pressing the key next to Enter on a German board shows the same position as a US board with a different character. That is a layout setting, not a fault.
- My Fn key does nothing here.
- Fn is usually handled inside the keyboard itself and never reaches the operating system, so no browser can see it. The keys it modifies, like brightness or volume, are often invisible for the same reason.
- Some combinations never show up at all.
- A few belong to the system rather than to any web page: the Windows or Command key on its own, Alt+Tab, Ctrl+Alt+Delete and the task manager shortcut are handled before a browser ever sees them. No web-based tester can check those, which is worth knowing before you conclude a key is dead.
- Is anything I type recorded?
- No. Key presses are matched against the layout drawn on screen and then forgotten. Nothing is stored and nothing is sent anywhere, which is why the page works with no account and no connection.