Easy HTML Question 69 of 229

What do async and defer do on a script tag?

Frontend Master · Speak this in 60–90 seconds · Faridabad & Delhi NCR

Call fetchPromise pending

NetworkWait off stack

Then / awaitUse the JSON

Both download the script without blocking HTML parse.

Why interviewers care about HTML:

HTML questions separate people

who only read docs from people who shipped.

Keep it short, concrete,

and tied to Frontend work.

Stay structured

Name the idea, why it exists, then one short example.

Close cleanly

End with when you use it and one common pitfall.

Before you speak the answer, walk the interviewer through these steps:

1
Both download the script
without blocking HTML parse.
2
Defer waits to execute
until the document is parsed and keeps order.
3
Async runs as soon
as the file arrives, so order is not guaranteed, which is fine for independent analytics.
4
Give an example
One tiny concrete case you can say aloud.
5
Common mistake
What juniors usually get wrong.
6
Close
When you pick this over the alternative.

Here's a short line you can speak, broken into clear beats:

Say this line

“Defer waits to execute until the document is parsed and keeps order.”

Break into beats

Deferwaitstoexecuteuntilthe

Speaking order

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Note: Adapt this scaffold to your own project — keep it under 60–90 seconds.

Both download the script without blocking HTML parse. Defer waits to execute until the document is parsed and keeps order.