System Design · Middle · Question 53 of 75

When does the browser send a CORS preflight request, and how can you avoid it?

✓Correct answer: For "non-simple" requests (e.g. PUT, JSON content type, custom headers); serving the API from the same origin avoids it
2Before every request
3Only for images

Explanation

The extra OPTIONS round trip adds latency. Access-Control-Max-Age lets browsers cache the preflight result.

Further reading

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