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- The async attribute is said to be a Boolean attribute.
- The async attribute is used to execute the script asynchronously depends upon its availability.
- The async attribute only presents with combination of src attribute. Because external script only use async attribute.
Syntax for async attribute in HTML:
<script src="source name" async></script>Applies To:
| Elements | Attribute |
|---|---|
| <script> | async |
Sample Coding for async Attribute in HTML:
Tryit<!DOCTYPE html>
<html>
<head>
<title>Wikitechy async attribute</title>
</head>
<body>
<script src="async_demo.js" async></script>
<h2>Welcome to Wikitechy!</h2>
</body>
</html>Code Explanation for async Attribute in HTML:
- src attribute is used to specify the external JavaScript file location as “async_demo.js”.
- async attribute is used to set the file parsing “async_demo.js” as asynchronously.
Output for async Attribute in HTML:
- The output shows the <h2> element (“Welcome to Wikitechy!”) and the alert message (“Hello wikitechy!”). Because the async attribute is set so the contents are loading asynchronously.
- If the async attribute not set the content loading synchronously so the content of <h2> is not loaded.
Browser Support for async Attribute in HTML:
 |
 |
 |
 |
 |
|---|---|---|---|---|
| Yes | 10.0 | 3.6 | Yes | Yes |