A 60 percent keyboard drops the keys a full board puts to the right and along the top. There is no function row, no Insert/Home/Page cluster, and usually no dedicated arrows. This page opens on that drawing. Escape is painted at the left of the number row, in the place a full-size board uses for the backtick. The separate backtick key is not on the drawing. F1 through F12 are not on it either. If you press a key and nothing lights, read the line under the grid before you call the switch dead. The line shows key, code, and keyCode for the event the browser actually got.
Layers are the reason a 60 percent test looks confusing. Fn, or a layer key the board labels with a padlock, often sends nothing by itself. It changes the next key. Arrows hidden on WASD or IJKL still arrive as ArrowLeft, ArrowUp, and the rest, if the firmware is sending arrow codes. This drawing has no arrow button, so those events light nothing and the readout is the whole test. Switch the drawing to TKL when you want to see the arrow buttons. A layer that types a backtick reports code Backquote, which also has no button here. The full tester still draws that key. The page does not remap the board and it does not write to the firmware.
Rollover is the other reason people open a compact board. The held list is every key the browser still considers down. Hold the keys you actually use together, such as W, A, S, D and two more. Many USB modes stop after six non-modifier keys. A seventh key that stays dark, while your finger is down, is that limit or a ghost, not a missing keycap on the drawing. Modifiers are often reported on top of the six. A key that is dark when pressed alone, here and in a text editor, is a dead switch. A key that works in an editor and not here usually means this page was not focused. Click the background and try again.
The bottom row on the drawing is the full-size modifier row: Control, the OS key, Alt, Space, and the menu key. A real 60 percent board is often shorter than that. Codes still light the matching button. A keycap printed Fn may never produce a code, which is normal. Space and Tab are kept from leaving the page while it is focused, so you can see them. The "most at once" number resets on reload, and the held list clears if the window loses focus, because browsers often skip the key-up when you leave.
This is not the laptop deck and it is not a MacBook. A laptop keeps a function row and a separate arrow cluster; that drawing is on the laptop tester. Command and Option labels, and the keys macOS tends to eat, are on the Mac tester. Use this page when the board in front of you has about sixty keys. Quote the code that never arrives if the failure follows the keyboard to a second computer.