Performance check
Render-blocking JavaScript
Finds external scripts in the <head> without defer, async or type="module".
- Category
- Performance
- Importance
- Medium importance
- Check id
- javascript-defer
How the result is decided
- PassNo render-blocking scripts in the head.
- WarningAt least one.
Why it matters
The browser stops building the page until such a script has downloaded and run, so visitors look at a blank screen for longer.
How to fix it
<script src="/app.js" defer></script>After the fix, open the page’s report and choose Run again to confirm it passes.