What's a good score?
Most people clicking normally land somewhere between 6 and 8 clicks per second. Get above 10 and you're clearly faster than average. Beyond that, it's usually technique rather than raw finger speed.
The duration makes a big difference. On the 1-second test you can go all out, so scores come out high. On 10 or 30 seconds your hand gets tired and your number drops. The longer tests are a fairer measure of how fast you can keep it up, which is what counts in most games.
Clicking techniques
Jitter clicking. You tense your forearm until your hand starts to vibrate and your finger taps along with it. Most people reach 10 to 14 CPS this way. It's tiring and puts real strain on your wrist, so don't do it for long.
Butterfly clicking. Two fingers take turns clicking the same button, usually index and middle finger. Easier to keep up than jitter clicking, and it can reach higher scores.
Drag clicking. You slide a finger across the mouse button so the friction makes it bounce very quickly. This can produce extreme numbers, but it depends heavily on the mouse. On some mice it simply doesn't work.
Whatever you try, take breaks. Some games and servers also limit or flag very high click speeds, so check the rules before you use these techniques there.
How the test counts your clicks
A click counts the moment the left mouse button goes down, not when you let go, so the counter keeps up with however fast you press. Right and middle clicks are ignored. You can also use Space or Enter while the box is selected; holding the key down counts once, not as a stream of repeats.
The timer starts on your first click and runs on the browser's high-precision clock, so a 5-second test really is 5 seconds. Your score is the number of clicks divided by the length of the test. When time is up the box locks for a moment, so one last frantic click doesn't start a new round by accident. Your best score for each duration is kept in this browser only.
Score suspiciously high?
If a single slow click sometimes counts as two, it's not you. It's your mouse. The switch under the button wears out over time and starts sending two signals for one press. It's one of the most common mouse faults, even on expensive gaming mice. Click slowly ten times and count along with the counter. If the numbers don't match, the switch is going. Keyboards get the same fault, called chattering, and the keyboard test counts every press so you can catch it.
Fixing a mouse that double clicks
Start with the software. Many gaming mice have a debounce or click delay setting in their own app; raising it a few milliseconds can hide a worn switch for a while. Also check that no macro or rapid-fire function is assigned to the button. The double-click speed setting in Windows or macOS has nothing to do with this fault.
If that doesn't help, the switch itself is worn. A short blast of compressed air under the button sometimes buys some time. A mouse still under warranty is usually replaced without discussion, because double clicking is a known fault. Out of warranty, a new switch can be soldered in if you're handy, but for most mice replacing the whole mouse is quicker. Buying a second-hand laptop? The used laptop check covers the touchpad and keyboard along with the rest.