Short answer: a mouse that doubles only sometimes is almost always the early stage of switch chatter — a contact that has begun to bounce but has not failed outright. Whether any single press doubles depends on things that change click to click, so the fault comes and goes instead of happening every time. A browser cannot look inside the switch, but it can catch the symptom when it fires: one deliberate press logging two click events a few milliseconds apart. With an intermittent fault the whole game is testing enough to catch it.
Why it happens only sometimes
Every mechanical mouse switch “bounces” a little when the contacts meet — they make and break contact several times over a few milliseconds before settling. That is normal, and the mouse firmware (and the operating system) apply a short debounce window that ignores those extra make/break events, so one press becomes one click. A healthy switch bounces well inside that window.
As a contact wears, oxidizes, or picks up contamination, its bounce gets longer and less predictable. Now some presses settle inside the debounce window (one click, as intended) and some ring on past it (a second click gets through). Which side of that line a given press lands on depends on how fast and hard you pressed, the exact contact geometry that press, dust or oxide on the surface, and even temperature. Early wear sits right at the boundary — so the doubling is intermittent. As wear progresses the switch crosses the line more often, and “sometimes” slowly becomes “most of the time.” That is general mechanical-switch behavior, not a verdict about your specific mouse.
Why a quick test can miss it
This is the trap with intermittent chatter: click five times, see it behave, and conclude the mouse is fine. But a fault that fires on one press in twenty will not show up in five clicks — you simply did not roll the dice enough times. A short clean run does not clear an intermittent fault; it only means it did not happen to fire during those clicks. Frequency is also information: a doubling every few clicks and a doubling once an hour are the same kind of fault at different stages of wear.
How to catch an intermittent fault in the browser
- Open the double-click check and set a low threshold — a value in milliseconds below which an adjacent click is flagged. A few milliseconds is far shorter than any deliberate double-click, so a flagged interval is a second event you did not make.
- Make many deliberate, separate single clicks on the affected button — dozens, not five. Do not double-click on purpose. The more single presses you make, the more chances an intermittent fault has to appear.
- Vary the press a little — speed and force — and try to reproduce the conditions where you actually notice the problem (after the machine has warmed up, in a particular app, when clicking quickly). Intermittent faults are often condition-dependent.
- Repeat across separate sessions. The check keeps your runs in local History, so you can accumulate evidence over a day or two instead of trusting a single run. One flagged doubling on a press you made once is real — it does not need to happen every time to count.
If you want the single-run walkthrough first, the 60-second double-click check covers one run, and the chatter result reference explains what the flagged numbers mean.
What the browser can and cannot tell you here
The check records real click events and the interval between them, and it flags intervals that are too short to be two separate deliberate clicks — that is the symptom of chatter, captured when it fires. It labels a flagged interval a review filter, not a hardware fault count, because a web page cannot open the mouse or measure the switch bounce directly. It also cannot measure the debounce window, polling rate, DPI, click latency, or temperature — a browser has no access to any of those, and a tool that claimed to would be guessing. The general limits are laid out in how we test. For an intermittent fault the one practical consequence is simple: you may need a lot of clicks to catch it.
If you confirm it
Once you have caught the doubling repeat, the fix guide walks through what to try, and if the mouse is under warranty the RMA / warranty evidence guide shows how to export a repeatable, timestamped report to attach to a claim.
The short intervals this check records are real button events observed in the browser; reading them as “chatter” is a symptom, not a hardware diagnosis. The open double-click input behavior dataset lists the reference numbers. Because an intermittent fault fires only some of the time, the signal that matters is a second event on a click you made only once — caught even once, and shown to repeat.