PreviewDrop for Next.js

Self-hosted deploy previews for Next.js

Push a branch, get a live preview URL. PreviewDrop builds your Next.js app in standalone mode, runs it as a real Node process, and posts the link to the pull request, usually within a couple of minutes — on your own infra, password-protected, flat-priced.

TL;DR

Set output: 'standalone' in next.config, connect your repo, push. PreviewDrop detects Next.js, builds the image and runs server.js behind a TLS-terminated subdomain. Full Node runtime — middleware, route handlers, ISR and server actions all work, and previews are password-protected by default.

What the build needs to do

You don't write this. PreviewDrop detects Next.jsfrom your repo and builds the container for you — a Dockerfile in your repo is not used. The reference below shows the install, build and start steps a working Next.js image needs. If detection gets one wrong, set the matching Install, Build or Start command in Project Settings. Your app must listen on $PORT.

Reference (not read by PreviewDrop)
FROM node:22-slim AS build
WORKDIR /app
COPY package*.json ./
RUN npm ci
COPY . .
RUN npm run build

FROM node:22-slim
WORKDIR /app
ENV NODE_ENV=production HOSTNAME=0.0.0.0
# Requires output: 'standalone' in next.config.{js,ts}
COPY --from=build /app/.next/standalone ./
COPY --from=build /app/.next/static ./.next/static
COPY --from=build /app/public ./public
EXPOSE 3000
CMD ["node", "server.js"]

Environment variables

Set these in the Variables tab of your PreviewDrop project. They're encrypted at rest and injected into every preview container at start.

Variable	Example value	Note
PORT	3000	PreviewDrop injects this; the standalone server.js reads it automatically.
DATABASE_URL	postgres://user:pass@host:5432/db	Server-side only env is read at runtime — safe to set here.
NEXT_PUBLIC_API_URL	https://api.example.com	NEXT_PUBLIC_* is inlined at BUILD time — see the gotcha below.

Common gotchas

Set output: 'standalone' in next.config

A standalone runtime runs only .next/standalone, which Next.js produces only when output: 'standalone' is set. Without it there’s no server.js to run and the container exits immediately.

NEXT_PUBLIC_* vars are baked at build time

Anything prefixed NEXT_PUBLIC_ is inlined into the client bundle during npm run build, not read at container start. Set those project variables before the build runs (they’re available as build args), or keep client-side config in non-secret runtime fetches. Server-only secrets are read at runtime and are fine to set normally.

Copy static and public into the standalone output

The standalone server.js does not include .next/static or public. Both must sit next to it (the reference build above copies them) or your CSS, JS chunks and images 404. If they are missing, set the Build and Start commands in Project Settings to do the same.

Bind to 0.0.0.0

Set HOSTNAME=0.0.0.0 (PreviewDrop sets it in the container) so the standalone server listens on all interfaces. The default can bind to localhost inside the container, which the proxy can’t reach.

Why not Vercel or Netlify?

Vercel is an excellent home for Next.js — PreviewDrop isn’t trying to replace it for everyone. It’s for teams who self-host Next.js (in Docker, on their own cloud, or next to a backend API), want password-protected previews to share with clients, prefer flat per-workspace pricing over per-seat, or run Next.js alongside a Django/Rails/Go service that needs previews too. One tool, every branch — frontend and backend.

Preview your Next.js app in 5 minutes

Connect a repo, push a branch, get a URL. No credit card, no trial clock.

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