Vercel Env Management

Vercel Env Management

Vercel is the source of truth for environment variables; your local .env* files are a cache of it, not the other way around. This skill keeps that cache honest: pull the right values for the right environment, add and remove vars without leaking secrets into git, and use OIDC so you never paste a long-lived cloud key anywhere. Get this wrong and you ship a preview build talking to a production database, or a NEXT_PUBLIC_ key that is stale because it was baked in at build.

This is one step in the vercel-platform ship-a-Next.js-app workflow. It is deliberately not a transcription of the vercel env man page - it sequences the commands into the order a real project needs them and flags the three mistakes that actually cost people an afternoon. Pair it with vercel-deploy-pipeline (which consumes these vars at build) and vercel-ai-gateway (which replaces a pile of per-provider keys with one).

Trigger eagerly: "sync my env", "pull env vars", "set a secret", "env var is undefined", "different value per environment", "my NEXT_PUBLIC var won't update", "keyless AWS/GCP access", "OIDC token".

The model: three environments, one variable name

Vercel scopes every variable to one or more environments:

• development - used by vercel dev and pulled into your local .env.local.
• preview - every non-production deployment (every branch/PR). You can scope a preview value to a single git branch with --git-branch.
• production - the deployment behind your production domain.
• custom environments (e.g. staging) - named, long-lived targets you create in the dashboard; addressed by name everywhere a built-in environment is.

The same name (DATABASE_URL) holds a different value per environment. That is the whole point: preview points at a branch database, production at the real one.

Step 1 - Link the project (once)

Every vercel env command operates on the linked project. Link before anything else; it writes .vercel/ (which is gitignored by the CLI):

vercel link

Step 2 - Pull the development env into a local file

vercel env pull writes the development variables to .env.local by default (Next.js, Astro, SvelteKit, Nuxt all read .env.local locally):

vercel env pull                 # -> .env.local (development env)
vercel env pull .env.local      # explicit, same thing
vercel env pull --yes           # overwrite without the confirm prompt (CI)

To inspect what production or preview actually has - to debug an "it works locally but not in prod" gap - pull that environment into a throwaway file and diff:

vercel env pull .env.production.local --environment=production
vercel pull --environment=preview --git-branch=my-feature  # branch-scoped preview

vercel pull (no env) also pulls project settings + env into .vercel/; use it in CI before vercel build. For just the dotenv file locally, vercel env pull is the one you want.

Step 3 - Add a variable to the right environment(s)

Never hand-edit a value into .env.local and expect it to deploy - that file is a local cache and is gitignored. Add it to Vercel:

vercel env add DATABASE_URL production          # prompts for the value
vercel env add DATABASE_URL preview             # a different value for preview
vercel env add DATABASE_URL development          # and for local `vercel dev`

Mark anything credential-shaped sensitive so its value can never be read back out of the dashboard or API (write-only after creation):

vercel env add STRIPE_SECRET_KEY production --sensitive

Pipe a value in for scripting (avoids the interactive prompt), and --force to overwrite an existing one:

printf '%s' "$VALUE" | vercel env add API_TOKEN production --sensitive
vercel env add API_TOKEN production --force      # replace existing value

Mind the budget: Vercel caps the combined size of all env vars at 64 KB per deployment (Edge-runtime consumers are tighter, around 5 KB per variable). If you are pushing against that, the fix is fewer/leaner vars - move big blobs of config into Edge Config or a store, not into the environment.

After adding or changing a var, re-pull so your local cache matches: vercel env pull.

Step 4 - List and remove

vercel env ls                       # all vars, which environments each targets
vercel env ls production            # filter to one environment
vercel env rm OLD_TOKEN production   # remove from one environment
vercel env rm OLD_TOKEN --yes        # skip the confirm prompt

Removing a var does not affect already-built deployments - it takes effect on the next build (see Step 6 for the redeploy rule).

Step 5 - Keyless cloud access with OIDC (stop storing cloud keys)

Do not put a long-lived AWS/GCP/Azure key in an env var if you can avoid it. With Secure Backend Access enabled, Vercel issues a short-lived VERCEL_OIDC_TOKEN (present at build time and as a request header at runtime) that you exchange for temporary cloud credentials. Nothing long-lived is stored, and tokens rotate automatically. This is the recommended pattern for talking to a cloud provider from a Vercel Function.

Pull the token for local dev like any other dev var. Note it is short-lived by design - a locally pulled VERCEL_OIDC_TOKEN is valid for about 12 hours, so a morning vercel env pull is part of the routine, not a one-time setup:

vercel link
vercel env pull        # brings down VERCEL_OIDC_TOKEN among the dev vars

Exchange it for AWS credentials with the first-party provider - no AWS_ACCESS_KEY_ID in your env at all:

// app/api/report/route.ts
import { S3Client } from '@aws-sdk/client-s3';
import { awsCredentialsProvider } from '@vercel/oidc-aws-credentials-provider';

const s3 = new S3Client({
  region: process.env.AWS_REGION,
  credentials: awsCredentialsProvider({
    roleArn: process.env.AWS_ROLE_ARN, // the IAM role Vercel's OIDC may assume
  }),
});

(The AWS provider lives in @vercel/oidc-aws-credentials-provider - npm i @aws-sdk/client-s3 @vercel/oidc-aws-credentials-provider. The older @vercel/functions/oidc import has been moved out.)

For GCP, feed getVercelOidcToken to a workload-identity external account client:

import { getVercelOidcToken } from '@vercel/oidc';
import { ExternalAccountClient } from 'google-auth-library';

const authClient = ExternalAccountClient.fromJSON({
  type: 'external_account',
  audience: `//iam.googleapis.com/projects/${process.env.GCP_PROJECT_NUMBER}/locations/global/workloadIdentityPools/${process.env.GCP_WORKLOAD_IDENTITY_POOL_ID}/providers/${process.env.GCP_WORKLOAD_IDENTITY_POOL_PROVIDER_ID}`,
  subject_token_type: 'urn:ietf:params:oauth:token-type:jwt',
  token_url: 'https://sts.googleapis.com/v1/token',
  service_account_impersonation_url: `https://iamcredentials.googleapis.com/v1/projects/-/serviceAccounts/${process.env.GCP_SERVICE_ACCOUNT_EMAIL}:generateAccessToken`,
  subject_token_supplier: { getSubjectToken: getVercelOidcToken },
});

The cloud-side setup (an IAM role / workload-identity pool that trusts Vercel's OIDC issuer with your team+project as the subject) is one-time and lives in your cloud console, not here. Once it trusts Vercel, you delete the stored key.

Aside: for AI providers specifically, you usually do not need any of this - the AI Gateway already accepts VERCEL_OIDC_TOKEN on Vercel and an AI_GATEWAY_API_KEY locally, so one credential covers every model. That belongs to vercel-ai-gateway.

Step 6 - The build-time inlining rule (NEXT_PUBLIC_*)

This is the single most common env surprise. NEXT_PUBLIC_-prefixed variables are inlined into the client bundle at build time - their values are literally string-replaced into the JavaScript when the build runs. Consequences:

• Changing a NEXT_PUBLIC_ value in the Vercel dashboard does nothing to a deployment that already built. You must redeploy to bake in the new value.
• They are public - anything in a NEXT_PUBLIC_ var ships to the browser. Never prefix a secret. (Marking it --sensitive does not make a NEXT_PUBLIC_ var private; the prefix wins.)
• Server-only vars (no prefix) are read at runtime from process.env inside Functions/Middleware, so updating them + redeploying - or in some cases just a new deployment - picks up the change without a rebuild caveat.

When someone reports "I updated the env var but the site still shows the old value," 90% of the time it is a NEXT_PUBLIC_ var and the fix is redeploy, not re-pull. Use the verifier below to catch leaks and stale-risk before they ship.

Quality bar

An env setup is done right only when all hold:

• .env.local (and any pulled .env.*.local) is gitignored and was produced by vercel env pull, never hand-authored as the source of truth.
• Every variable that differs by stage is set in each environment it is needed in - a value present only in production silently becomes undefined in preview.
• Every credential-shaped var is --sensitive; no secret carries a NEXT_PUBLIC_ prefix.
• Cloud access uses OIDC where the provider supports it; long-lived cloud keys are removed once the role trust is in place.
• After any dashboard change to a NEXT_PUBLIC_ var, the app was redeployed (not just re-pulled) before anyone trusts the new value.

Do NOT

• Do NOT commit .env.local / .env.production.local. They hold real secrets and are gitignored for a reason; pulling them is fine, committing them is a leak.
• Do NOT treat the local file as the source of truth. Edit on Vercel (vercel env add), then vercel env pull to refresh the cache.
• Do NOT put a secret behind NEXT_PUBLIC_ - it is shipped to every browser, and --sensitive cannot save it.
• Do NOT expect a NEXT_PUBLIC_ value change to take effect without a redeploy; it was inlined at build time.
• Do NOT set one shared value across all environments and assume preview is safe - a preview build with a production DATABASE_URL writes to prod.
• Do NOT paste long-lived AWS/GCP keys into env vars when OIDC + a trusted role does the same job with rotating short-lived credentials.
• Do NOT own the deploy/promote step here - that is vercel-deploy-pipeline.
• Do NOT configure runtime/region/ISR caching here (vercel-edge-and-isr), WAF / bot rules (vercel-firewall-and-botid), or bundle/runtime perf (next-on-vercel-perf) - this skill stops at the variables themselves.

Verifier: lint your dotenv + Vercel env wiring

Self-contained Node script, no dependencies. Save as env_check.mjs and run from your repo root with node env_check.mjs. It parses .env.local, flags secrets that are publicly inlined, secrets that are not gitignored, and (optionally) any variable your code reads via process.env.X that is missing from the pulled file.

// Vercel env wiring linter. Run from repo root: node env_check.mjs
// Reads .env.local (or arg 1), checks it against your source for missing vars.
import { readFileSync, existsSync, readdirSync, statSync } from 'node:fs';
import { join, extname } from 'node:path';

const envFile = process.argv[2] || '.env.local';
const SECRETY = /(SECRET|TOKEN|KEY|PASSWORD|PRIVATE|DSN|CREDENTIAL)/i;

function parseDotenv(text) {
  const out = {};
  for (const line of text.split('\n')) {
    const m = line.match(/^\s*([A-Z0-9_]+)\s*=/i);
    if (m && !line.trimStart().startsWith('#')) out[m[1]] = true;
  }
  return out;
}

function gitignored(name) {
  if (!existsSync('.gitignore')) return false;
  const ig = readFileSync('.gitignore', 'utf8');
  return ig.split('\n').some((l) => l.trim() === name || l.trim() === '.env*.local' || l.trim() === '.env.local');
}

function walk(dir, acc = []) {
  for (const e of readdirSync(dir)) {
    if (e === 'node_modules' || e === '.next' || e === '.git' || e === '.vercel') continue;
    const p = join(dir, e);
    const st = statSync(p);
    if (st.isDirectory()) walk(p, acc);
    else if (['.ts', '.tsx', '.js', '.jsx', '.mjs'].includes(extname(p))) acc.push(p);
  }
  return acc;
}

const problems = [];
const notes = [];

if (!existsSync(envFile)) {
  console.error(`No ${envFile} found. Run: vercel link && vercel env pull`);
  process.exit(1);
}

const present = parseDotenv(readFileSync(envFile, 'utf8'));
const names = Object.keys(present);

// 1) Secrets that are publicly inlined.
for (const n of names) {
  if (n.startsWith('NEXT_PUBLIC_') && SECRETY.test(n)) {
    problems.push(`${n}: secret-shaped but NEXT_PUBLIC_ -> inlined into the browser bundle.`);
  }
}

// 2) The env file itself must be gitignored.
if (!gitignored(envFile)) {
  problems.push(`${envFile} is not gitignored. Add ".env*.local" to .gitignore before committing.`);
}

// 3) Vars the code reads but the pulled file is missing.
const referenced = new Set();
for (const file of walk(process.cwd())) {
  const src = readFileSync(file, 'utf8');
  for (const m of src.matchAll(/process\.env\.([A-Z0-9_]+)/g)) referenced.add(m[1]);
}
const SYSTEM = /^(NODE_ENV|VERCEL|VERCEL_|CI|npm_)/;
for (const r of referenced) {
  if (!present[r] && !SYSTEM.test(r)) {
    notes.push(`${r}: read via process.env but absent from ${envFile}. Set it: vercel env add ${r} <env>, then re-pull.`);
  }
}

console.log(`Checked ${names.length} vars in ${envFile}, ${referenced.size} process.env refs in source.`);
if (problems.length) {
  console.log('\nPROBLEMS (fix before deploy):');
  for (const p of problems) console.log('  x ' + p);
}
if (notes.length) {
  console.log('\nMISSING LOCALLY (set on Vercel + re-pull, or these are server-only prod vars):');
  for (const n of notes) console.log('  ? ' + n);
}
if (!problems.length && !notes.length) console.log('\nOK: no leaked secrets, file is gitignored, every referenced var is present.');
process.exit(problems.length ? 1 : 0);

Worked example output

Given a .env.local that contains NEXT_PUBLIC_STRIPE_KEY=sk_live_... (a secret wrong-prefixed) and source that reads process.env.DATABASE_URL (never pulled):

Checked 6 vars in .env.local, 4 process.env refs in source.

PROBLEMS (fix before deploy):
  x NEXT_PUBLIC_STRIPE_KEY: secret-shaped but NEXT_PUBLIC_ -> inlined into the browser bundle.

MISSING LOCALLY (set on Vercel + re-pull, or these are server-only prod vars):
  ? DATABASE_URL: read via process.env but absent from .env.local. Set it: vercel env add DATABASE_URL <env>, then re-pull.

Read it: rename NEXT_PUBLIC_STRIPE_KEY to STRIPE_SECRET_KEY, re-add it as --sensitive, and read it only in a Function - never the client. Then vercel env add DATABASE_URL development (and preview/production) and vercel env pull so the local cache is complete. A clean run is the gate before you hand off to vercel-deploy-pipeline.

Template: env-inventory

Keep this table in the repo (README or docs/env.md) so every var's scope, sensitivity, and inlining are documented. The verifier checks wiring; this checks intent.

VERCEL ENV INVENTORY. [FILL: project name]

NAME                     DEV  PREVIEW  PROD  SENSITIVE  CLIENT?(NEXT_PUBLIC)  SOURCE
[FILL: DATABASE_URL]      y    y(branch) y     y          n                    Neon (Marketplace)
[FILL: STRIPE_SECRET_KEY] y    y        y     y          n                    Stripe dashboard
[FILL: NEXT_PUBLIC_URL]   y    y        y     n          y (redeploy on change) computed per env
[FILL: AWS_ROLE_ARN]      y    y        y     n          n                    OIDC role (no key stored)

RULES
  - SENSITIVE=y  -> added with `--sensitive`, write-only, never echoed.
  - CLIENT=y     -> NEXT_PUBLIC_, public + inlined at build; REDEPLOY to change.
  - Any cloud credential -> prefer OIDC role over a stored key.
  - .env*.local is gitignored; Vercel is the source of truth.