Next.js · Middle · Question 57 of 75

Why can't you call `(await cookies()).set(...)` while rendering a server component?

✓Correct answer: Cookies can be set only in Server Actions, Route Handlers or proxy.ts - headers may already be streaming during render
2cookies() is read-only everywhere
3Setting cookies requires a client component

Explanation

HTTP headers must be sent before the body. Render may stream, so Next.js only allows writing cookies where the response is fully controlled.

Further reading

Next.js: cookies ↗

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