Rocket Validator integrates the W3C Validator HTML checker into an automated web crawler.
HTML issues tagged as defer.
The defer and async boolean attributes of the <script> element control how an external script should be executed once it has been downloaded. These attributes only make sense when referring to external scripts, so a src attribute must also be present to specify the location of the script.
<script defer src="app.js"></script>
If your script is not external, and is inlined within the HTML document, then you should remove the defer attribute, like in this example:
<script> console.log("hello"); </script>
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