MouseEvent.y is a read-only number: the mouse’s vertical position in CSS pixels, measured from the viewport top edge. Per MDN, it is an alias for clientY.
Read the notes below before you rely on this property. Prefer feature detection when support is limited.
Use event.y. Start with this line.
const y = mouseEvent.y;| Call | What it does |
|---|---|
const y = mouseEvent.y; | Primary signature. |
Built into the browser. Read event.y on a MouseEvent — no import required.
const y = mouseEvent.y;| Parameter | Description |
|---|---|
| Mouse / pointer event | Required. Source that exposes y |
| Return Value | Description |
|---|---|
| * | The current value of event.y. |
y on MovePrint viewport X and Y while the mouse moves.
document.addEventListener("mousemove", (event) => {
console.log(event.x, event.y);
});mousemove.event.x / event.y are viewport coordinates.clientX / clientY.y === clientYConfirm MDN’s alias rule with a one-line equality check.
document.addEventListener("click", (event) => {
console.log(event.y);
console.log(event.clientY);
console.log(event.y === event.clientY);
});MouseEvent.y and clientY show the same number.===. true means the alias works in this browser.y or clientY consistent in your project.y vs pageYSee when viewport Y and document Y stay equal — and when they diverge.
document.addEventListener("click", (event) => {
console.log({
y: event.y,
clientY: event.clientY,
pageY: event.pageY,
scrollY: window.scrollY
});
});y and clientY stay locked together.scrollY === 0, pageY matches too.pageY grows; y stays viewport-based.y; document markers → pageY.MouseEvent.y is Baseline Widely available (MDN: since April 2017). It is defined in the CSSOM View Module as an alias of clientY.
Supported across modern Chrome, Firefox, Safari, and Edge. Same practical availability as clientY for viewport Y.
Bottom line: Safe for production. Prefer clientY if your team wants the longer, more explicit name; values match on supporting browsers.
Check whether modifier keys like Shift or CapsLock were active for the event.
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