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How does Next.js decide between static and dynamic rendering at build time?

Q: How does Next.js decide between static and dynamic rendering at build time?

**TL;DR.** At build, Next.js **analyzes each route**: if it uses no dynamic functions and only cached data, it's **prerendered statically**; if it uses cookies() / headers() / searchParams or **uncached** fetches, it's marked **dynamic**. Segment config ( dynamic ) can force either mode. build analysis no dynamic API + cached → STATIC<

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Automatic detection based on APIs and data usage.

nextjsrenderingstaticdynamic

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Reading the build output

$ next build
Route (app)                     Size
○ /                             (Static)   prerendered as static HTML
● /blog/[slug]                  (SSG)      prerendered via generateStaticParams
ƒ /dashboard                    (Dynamic)  server-rendered on demand
# ○ Static  ● SSG  ƒ Dynamic — check this to catch accidental dynamic routes

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