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