defer vs async on your scripts

defer vs async on your scripts

Both keep a script from blocking your page, which protects FCP and LCP (how fast text and images appear). The difference is timing. async runs each script the instant it arrives, in any order. defer waits until the page is built, then runs them in order.

Think of async as guests barging in whenever, and defer as a calm seating plan.

When each fits:
— A script that depends on others, or touches the page layout: defer, so order stays correct.
— A standalone tag like analytics that needs nothing else: async is fine.

Try this: look at your <script> tags in the page head. Any without defer or async is render-blocking. Add defer as your safe default. It rarely breaks anything.