What headers are involved in a CORS preflight?
PICTURE THIS: BROWSER VS ATTACKER
Simple meaning
A non-simple request triggers OPTIONS first.
WHY — Browser instead of guessing?
Why interviewers care about Browser:
who only read docs from people who shipped.
and tied to Frontend work.
Name the idea, why it exists, then one short example.
End with when you use it and one common pitfall.
STEPS — What happens step by step?
Before you speak the answer, walk the interviewer through these steps:
- 1A non-simple request triggers
OPTIONS first.
- 2The server should answer
Access-Control-Allow-Origin, Methods, and Headers, and optionally Max-Age.
- 3Authorization headers and JSON
content-type are typical reasons a GET becomes a preflight.
- 4Give an example
One tiny concrete case you can say aloud.
- 5Common mistake
What juniors usually get wrong.
- 6Close
When you pick this over the alternative.
EXAMPLE — See it in action
Here's a short line you can speak, broken into clear beats:
Note: Adapt this scaffold to your own project — keep it under 60–90 seconds.
Key takeaway
A non-simple request triggers OPTIONS first. The server should answer Access-Control-Allow-Origin, Methods, and Headers, and optionally Max-Age.