HTML <script> defer Attribute

Example

<script src="demo-defer.js" defer></script>

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Meaning

The defer attribute specifies that the browser might defer execution of the script enclosed by the <script> element.

Notes:

• async attribute is present: The script is downloaded in parallel to parsing the page, and executed as soon as it is available.
• defer attribute is present (and not async attribute): The script is downloaded in parallel to parsing the page, and executed after the page has finished parsing.
• Absence of async or defer: The script is downloaded and executed immediately, blocking parsing until the script is completed.
• The async attribute is only used for external scripts.

Standard Syntax

HTML: <script defer></script>

XHTML: <script defer="defer"></script>

Attribute Values