Short answer: open the mouse button test and press each button on the mouse in turn. The test registers a press the moment the browser receives the click, and labels it Left, Middle or Right (any extra button your browser reports shows up as Button N). The button that never registers, while the others do, is the one that has stopped working. That comparison — one button silent while its neighbours respond on the same page, same mouse, same session — is the whole diagnosis.
Check which button in the browser
- Open the mouse test and click left, middle and right once each. Each press that reaches the browser lights up its label, so you immediately see which ones work.
- Press the suspect button several times, firmly and deliberately. If it never registers while the others do, the fault is that button — not your hand, not the page.
- If your mouse has side (back/forward) buttons, press those too. A browser can only see them if the system passes them through as ordinary button events; many mice route side buttons through their own driver, so a side button that does nothing here may simply be remapped rather than broken.
- Watch for the opposite failure while you are there: a single press that registers twice is not a dead button but double-click chatter, a different fault with its own check.
What a click “not registering” can mean
A button that does not respond is a symptom with several possible causes, and the browser test tells you which button, not which cause. In general terms, a dead click usually comes down to one of these:
- A worn or failed switch. Mechanical switches wear out; a contact that no longer closes reliably produces presses that do not register. This is the mirror image of chatter, where a worn contact registers too many events.
- A driver or remap. Gaming-mouse software can reassign or disable a button. A button that does nothing everywhere but is set to “disabled” or a macro in its software is working exactly as configured.
- Connection or power. A flaky cable, a failing USB port, a low wireless battery, or a loose receiver can make inputs drop — sometimes one button first, sometimes intermittently.
- Software swallowing the click. A specific app, an overlay, or a stuck modifier can absorb a button in one place while it works elsewhere — which is why testing in a neutral page matters.
Narrow it down: button, mouse, or system
Once the test shows which button is silent, a few quick swaps tell you how far the problem goes. Try the same button in another program — if it works there but not in the test, or vice versa, the mouse hardware is probably fine and something in software is intercepting it. Plug the mouse into a different USB port, and if you can, try a different mouse on the same port: if the second mouse is fine, the port is not the problem. If the same physical button fails across ports, apps, and a reboot, it is most likely the button itself.
What the browser can and cannot tell you
The mouse test can confirm, honestly, whether a click event for a given button reaches the browser: it shows Left, Middle and Right registering, plus any extra button the system reports as Button N. That is enough to isolate which button is not responding. It cannot open the mouse or measure the switch, so it cannot tell you why a button is dead — worn switch, cable, driver, or battery all look the same from the page: no event. It also cannot measure polling rate, DPI, or click latency; a browser has no access to any of those, and a tool that claimed to would be guessing. The general limits are set out in how we test. One practical note: right-clicking normally opens the context menu, which the test suppresses while it is running so your right-button presses are counted instead of eaten by the menu.
If a run keeps getting cut short
If the test seems to miss presses in bursts rather than on one specific button, the problem may not be the button at all — a background focus change or a switch away from the tab can interrupt input capture. The interrupted-test guide explains what causes that and how to get a clean run, so you do not blame a button for a dropped session.
This check reports real button events observed in the browser and tells you which button is or is not registering; it does not diagnose the hardware cause. Confirm the fault by comparing the dead button against the ones that still work, across a couple of apps and ports, before concluding the button itself has failed.