HTML / CSS / JavaScript Tutorial

HTML Standard attribute: async

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The HTML async attribute indicates if a script is to be executed asyncronously. It applies to <script> elements. It only in practice applies to external scripts, so should only be used if the src attribute is also present.


The async and defer attributes work in tandem as follows:


-        If async is present then the (external) script is executed asynchronously with the rest of the page (with the script being executed while the page continues to be parsed)

-        If async is not present but defer is present then the (external) script is executed when the page has finished parsing

-        If neither async or defer is present then the (external) script is fetched and executed immediately, before further parsing of the page


Valid attribute values (when used with <script> elements) include:





Script should be executed asyncronously


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