---
source: https://iinventedlight.com/library/notes/nextjs-environment-variables.md
title: "Environment variables in Next.js"
license: CC-BY-4.0
license_url: https://creativecommons.org/licenses/by/4.0/
source_license: "MIT (vercel/next.js); prose restates cited source lines in own words"
license_family: nextjs-mit
attribution: "Summary by iinventedlight (AI-assisted). Sources: Next.js docs, Environment variables, MIT (vercel/next.js); Next.js docs, env, MIT (vercel/next.js). Copyright (c) 2025 Vercel, Inc. MIT (https://raw.githubusercontent.com/vercel/next.js/canary/license.md)."
author: "iinventedlight (synthesis of cited sources); text drafted with AI assistance"
date: 2026-11-09
status: published
approved_by: "Cole Withington, 2026-11-09 13:04 PT: \"Yes, publish all 33 Next.js drafts\""
checked_on: 2026-11-09
as_of: 2026-11-09
confidence: medium
untested: "No Next.js app was run for this note; only the fetched documentation pages were read."
category: coding-references
topic_area: "code-web: Next.js config"
tags: [nextjs, env]
client: Librarian
sources:
  - id: S1
    title: "Environment variables"
    publisher: Next.js docs
    url: https://nextjs.org/docs/app/guides/environment-variables
    accessed: 2026-11-09
    license: "MIT (vercel/next.js)"
  - id: S2
    title: "env"
    publisher: Next.js docs
    url: https://nextjs.org/docs/app/api-reference/config/next-config-js/env
    accessed: 2026-11-09
    license: "MIT (vercel/next.js)"
---
# Environment variables in Next.js

**Answer:** Next.js loads `.env` files. Variables stay on the server by default; prefix with `NEXT_PUBLIC_` for the browser.

## See also

- [nextjs-proxy](https://iinventedlight.com/library/notes/nextjs-proxy/)
- [nextjs-static-exports](https://iinventedlight.com/library/notes/nextjs-static-exports/)

## Claims

- id: C1
  claim: Next.js has built-in env support.
  source: S1
  evidence: "Next.js comes with built-in support for environment variables, which allows"

- id: C2
  claim: Bundle browser vars with NEXT_PUBLIC_.
  source: S1
  evidence: "[Bundle environment variables for the browser by prefixing with `NEXT_PUBLIC_`](#bundling-environment-variables-for-the-browser)"

- id: C3
  claim: Default env vars stay on the server.
  source: S1
  evidence: "**By default, environment variables are only available on the server**."

- id: C4
  claim: next.config env inlines values at build time.
  source: S2
  evidence: "Next.js will replace `process.env.customKey` with `'my-value'` at build time."

## Sources

- [S1] Environment variables. Next.js docs. https://nextjs.org/docs/app/guides/environment-variables . License: MIT (vercel/next.js). Accessed 2026-11-09.

- [S2] env. Next.js docs. https://nextjs.org/docs/app/api-reference/config/next-config-js/env . License: MIT (vercel/next.js). Accessed 2026-11-09.


License: this note is CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Summary by iinventedlight (AI-assisted). Copyright (c) 2025 Vercel, Inc. Sources: Next.js docs (vercel/next.js on GitHub / nextjs.org), MIT (https://raw.githubusercontent.com/vercel/next.js/canary/license.md). Text was condensed and changed from the originals.

---

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