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Nitro — The Server Engine

Deploy Your Server Anywhere — Same Code

Nitro — The Server Engine

Nitro is Nuxt's universal server runtime — the same source builds for Node, Cloudflare Workers, Vercel Edge, Netlify, Deno, and more.

4 min read Level 2/5 #nuxt#nitro
What you'll learn
  • Recognize the .output/ directory produced by nuxi build
  • Switch deploy targets by setting the Nitro preset
  • Know which features are portable versus preset-specific

Underneath Nuxt’s server pages and /api routes sits Nitro — a tiny, portable runtime built on h3. Nitro is the reason the same code can run on AWS Lambda, Cloudflare Workers, and a plain Node process.

What nuxi build Produces

Run npx nuxi build and you’ll get an .output/ directory:

.output/
  public/             # static assets and prerendered pages
  server/
    index.mjs         # the runtime entry
    chunks/           # treeshaken handler code

The shape of that folder depends on the preset. For Node, it’s a self-contained ESM bundle you can run with node .output/server/index.mjs.

Switching Presets

Nitro auto-detects the target (Vercel, Netlify, etc.) based on env vars and file presence. Force it explicitly when you need to:

// nuxt.config.ts
export default defineNuxtConfig({
  nitro: {
    preset: 'cloudflare-pages',
  },
})

Common presets:

  • node-server — long-running Node.
  • vercel, vercel-edge — Vercel functions / edge.
  • netlify, netlify-edge — Netlify functions / edge.
  • cloudflare-pages, cloudflare-workers — Cloudflare.
  • deno-deploy, bun — alternative runtimes.

Portable vs Preset-Specific

Portable across presets:

  • defineEventHandler, h3 helpers, fetch, Web standards.
  • server/api, server/middleware, server/utils.

Preset-specific (with caveats):

  • Node-only modules (fs, path) — fine on Node, broken on edge runtimes.
  • Database drivers that need TCP sockets — won’t run on Workers without HTTP proxies (e.g. Neon, PlanetScale serverless).

Treeshaking

Nitro removes unused server code per preset. If a handler isn’t reachable from any route, it’s dropped from the bundle. This keeps cold starts fast on edge runtimes.

server/api Deep Dive →