The answer
defer. It is non-blocking, executes in order, and runs after the DOM is ready. Use async only for independent scripts like analytics and ads.
async and defer Best Practices
Should you use async or defer for most scripts?
More FAQs in async and defer Best Practices
In the <head>. This starts the download early (in parallel with HTML parsing) while deferring execution until after parsing. This is faster than placing scripts at the bottom of <body>.
Yes. <script type='module'> is automatically deferred. You do not need to add the defer attribute. The script downloads in parallel and executes after parsing.
No. async does not guarantee execution order. If script B depends on A, use defer for both. defer guarantees order.
Still have questions?
Browse all our FAQs or reach out to our support team
Want to upskill yourself?
Your learning library
Small steps. Big possibilities.
Find your next course. Build something great.