Sometimes we want to load the CSS asynchronously to reduce the intial page load and you can do the same by adding media="print" onload="this.media='all' to the link as below.

<link rel="stylesheet" href="/path/to/my.css" media="print" onload="this.media='all'">

Let’s dive into the details of the above:

• The link’s media attribute is set to print.
• print is a media type that applies to print-based media or when the user tries to print the page.
• By using media="print", the CSS file loads asynchronously (since it’s not needed immediately for screen display).
• However, we still want to apply the styles to the page for screen use.
• To achieve this, we can use the onload attribute to change the link’s media to all once it finishes loading.

References

filamentgroup