W3Schools Tryit Editor

<!DOCTYPE html>
<html>
<head>
<meta name="viewport" content="width=device-width, initial-scale=1">
<style>
.tooltip {
  position: relative;
  display: inline-block;
}

.tooltip .tooltiptext {
  visibility: hidden;
  width: 140px;
  background-color: #555;
  color: #fff;
  text-align: center;
  border-radius: 6px;
  padding: 5px;
  position: absolute;
  z-index: 1;
  bottom: 150%;
  left: 50%;
  margin-left: -75px;
  opacity: 0;
  transition: opacity 0.3s;
}

.tooltip .tooltiptext::after {
  content: "";
  position: absolute;
  top: 100%;
  left: 50%;
  margin-left: -5px;
  border-width: 5px;
  border-style: solid;
  border-color: #555 transparent transparent transparent;
}

.tooltip:hover .tooltiptext {
  visibility: visible;
  opacity: 1;
}
</style>
</head>
<body>

<p>Click on the button to copy the text from the text field. Try to paste the text (e.g. ctrl+v) afterwards in a different window, to see the effect.</p>

<div class="tooltip">
<button onclick="myFunction()" onmouseout="outFunc()">
  <span class="tooltiptext" id="myTooltip">Copy to clipboard</span>
  Copy text
  </button>
</div>

function outFunc() {
  var tooltip = document.getElementById("myTooltip");
  tooltip.innerHTML = "Copy to clipboard";
}
</script>
</body>
</html>

​x
 
<!DOCTYPE html><html><head><meta name="viewport" content="width=device-width, initial-scale=1"><style>.tooltip {  position: relative;  display: inline-block;}​.tooltip .tooltiptext {  visibility: hidden;  width: 140px;  background-color: #555;  color: #fff;  text-align: center;  border-radius: 6px;  padding: 5px;  position: absolute;  z-index: 1;  bottom: 150%;  left: 50%;  margin-left: -75px;  opacity: 0;  transition: opacity 0.3s;}​.tooltip .tooltiptext::after {  content: "";  position: absolute;  top: 100%;  left: 50%;  margin-left: -5px;  border-width: 5px;  border-style: solid;  border-color: #555 transparent transparent transparent;}​.tooltip:hover .tooltiptext {  visibility: visible;  opacity: 1;}</style></head><body>​<p>Click on the button to copy the text from the text field. Try to paste the text (e.g. ctrl+v) afterwards in a different window, to see the effect.</p>