Getting mouse location in canvas [duplicate]

The accepted answer will not work every time. If you don’t use relative position the attributes offsetX and offsetY can be misleading.

You should use the function: canvas.getBoundingClientRect() from the canvas API.

  function getMousePos(canvas, evt) {
    var rect = canvas.getBoundingClientRect();
    return {
      x: evt.clientX - rect.left,
      y: evt.clientY - rect.top
    };
  }
  canvas.addEventListener('mousemove', function(evt) {
    var mousePos = getMousePos(canvas, evt);
    console.log('Mouse position: ' + mousePos.x + ',' + mousePos.y);
  }, false);