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HTML <script> tag : A script that will be downloaded in parallel to parsing the page, and executed as soon as it is available
The async
attribute is a boolean attribute.
If the async
attribute is set, the script is
downloaded in parallel to parsing the page, and executed as soon as it is
available. The parsing of the page is interrupted once the script is downloaded
completely, and then the script is executed, before the parsing of the rest of
the page continues.
async
attribute is only for external scripts (and should only be used if the
src
attribute is present).
async
is present: The script is
downloaded in parallel to parsing the page, and executed as soon as it is
available (before parsing completes)
defer
is present (and not async
): The
script is downloaded in parallel to parsing the page, and executed after the page has finished parsingasync
or
defer
is present: The script is downloaded and executed immediately,
blocking parsing until the script is completedThe numbers in the table specify the first browser version that fully supports the attribute.
Attribute | |||||
---|---|---|---|---|---|
async | 8.0 | 10.0 | 3.6 | 5.1 | 15.0 |
❮ HTML <script> tag