HTML defer Attribute
Definition and Usage
defer attribute is a boolean attribute.
When present, it specifies that the script is executed when the page has finished parsing.
defer attribute is only for external scripts (should only be used if the
src attribute is present).
Note: There are several ways an external script can be executed:
asyncis present: The script is executed asynchronously with the rest of the page (the script will be executed while the page continues the parsing)
asyncis not present and
deferis present: The script is executed when the page has finished parsing
- If neither
deferis present: The script is fetched and executed immediately, before the browser continues parsing the page
defer attribute can be used on the following element:
A script that will not run until after the page has loaded:
<script src="demo_defer.js" defer></script>Try it Yourself »
The numbers in the table specify the first browser version that fully supports the attribute.