There are two ways to remove the type attribute from your link and script tags depending on your version of WordPress. I’ll show you both ways below.
Pre WordPress 5.3
In versions below WordPress 5.3 we have to manually remove the attributes by changing the tags them self like shown below.
Here we register a callback function called optimize_style_tags to the style_loader_tag hook. The optimize_style_tags will now get called for each link tag and we use it to return a new link tag string that doesn’t contain the type attribute.
We do the same thing for the script tags by registering a callback function called optimize_script_tags tot the script_loader_tag hook.
Using conditional link or script tags
If you are adding conditional link or script tags using the wp_style_add_data function you will have to change the code above to use str_replace like shown below. Otherwise the conditional tags will be removed.
Post WordPress 5.3
As you can see it takes quite a bit of code to remove a simple attribute from the link and script tags. The nice people in this Trac issue thought so too. So as of WordPress 5.3 there is a build in option for this as shown below.
With the code above we register a function called register_html_support to the after_setup_theme hook. Inside the register_html_support function we make a call to the add_theme_support function to enable theme support for Html5. As the second parameter we pass an array containing the new ‘script’ and ‘style’ options.
Now there is a good chance your theme is already registering support for Html5 in which case you can now just add the ‘script’ and ‘style’ options.
With the ‘script’ and ‘style’ options added WordPress will automatically remove the type attributes from the link and script tags.
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Thanks for reading