Core answer
Start here. This is the direct spoken answer to practice first.
Overview
A fresh nonce strengthens script policy but changes how pages can be rendered and cached.
A nonce-based CSP creates a unique unpredictable nonce per request and allows only scripts carrying that nonce under the policy. Next.js can read the nonce from the request CSP header and apply it to framework scripts. Because the nonce does not exist at build time, affected pages require dynamic rendering rather than a reusable static response.