HTML defer Attribute

The HTML "defer" attribute specifies that a script is executed when a page has finished the parsing. It is a boolean attribute. This attribute works for external scripts and must be used only when the "src" attribute is present.

There isn’t any difference between HTML 4.01 and HTML5. In XHTML, the "defer" attribute must be specified as <script defer=”defer”> as attribute minimization is forbidden.

You can use this attribute on the <script> element.

An external script can be executed in the following ways:

  • When "async" is present, the script will be executed asynchronously while the page continues the parsing.
  • When "async" is not present but "defer" is present, the script will be executed when the page finishes the parsing.
  • When neither "async" or "defer" is present, the script will be executed immediately before the browser continues the parsing.


<script src="example.js" defer></script>

Example of the HTML "defer" attribute:

<!DOCTYPE html>
    <title>Title of the documnet</title>
    <script src="example.js" defer></script>
    <noscript>Sorry, your browser does not support JavaScript!</noscript>
    <p>The "defer" attribute specifies that the script should be executed later. This way the script can request information from the paragraph.</p>

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