Netlify: env vars not loading in functions [2026 fix]

Env vars undefined in Netlify Functions? Deploy your netlify.toml config and rebuild—Functions don't read .env files at runtime.

TL;DR

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Common Error Messages

Here are exact console outputs you'll see at 2am:

``` Uncaught ReferenceError: process.env.STRIPE_KEY is not defined at /var/task/stripe-handler.js:12:15 ```

``` TypeError: Cannot read property 'API_URL' of undefined at Object.<anonymous> (/var/task/.netlify/functions/api-proxy.js:3:5) ```

``` Failed to initialize: process.env.DATABASE_URL returned undefined Environment not available in function context ```

``` ERR: Your function tried to access process.env.JWT_SECRET but it's not in the Netlify runtime. ```

``` [ERROR] Runtime error in function at deployment: REACT_APP_API is undefined ```

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Broken vs. Fixed Code

❌ BROKEN: Relying on .env file

```javascript // netlify/functions/stripe-webhook.js require('dotenv').config();

const stripe = require('stripe')(process.env.STRIPE_KEY); // ↑ Returns undefined because .env isn't loaded in Netlify runtime

exports.handler = async (event) => { return { statusCode: 200, body: 'OK' }; }; ```

✅ FIXED: Variables declared in netlify.toml

```toml

netlify.toml

[functions] node_bundler = "esbuild"

[[functions]] name = "stripe-webhook" environment = { STRIPE_KEY = "sk_live_...", NODE_ENV = "production" } ```

```javascript // netlify/functions/stripe-webhook.js const stripe = require('stripe')(process.env.STRIPE_KEY); // ✓ Now properly available from netlify.toml

exports.handler = async (event) => { const session = await stripe.checkout.sessions.create({...}); return { statusCode: 200, body: JSON.stringify(session) }; }; ```

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Why This Happens

Netlify Functions run in AWS Lambda-based containers. The .env file exists only on your local machine and in your Git repository (if accidentally committed—don't do that). At deployment:

1. Your code is deployed but .env stays local 2. Function runtime spins up without access to .env 3. process.env.YOUR_VAR returns undefined 4. Your app crashes at 2am

Version note: This behavior is consistent across Netlify Functions from 2024–2026 and applies to Node.js 18.x, 20.x, and 22.x runtimes.

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Solution: Three Working Methods

Method 1: netlify.toml (Recommended for development)

```toml [[functions]] name = "api-proxy" environment = { API_URL = "https://api.example.com", API_KEY = "key_123" } ```

Method 2: Netlify UI Dashboard

1. Site settings → Build & deploy → Environment 2. Click "Edit variables" 3. Add key-value pairs (available to all functions) 4. Redeploy site

Method 3: Netlify CLI

```bash netlify env:set STRIPE_KEY sk_live_xxx netlify deploy --prod ```

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Critical: Verify Your Deploy

After pushing changes:

```bash

Check that netlify.toml is committed

Trigger rebuild

Check function logs

Deploy logs should show your variables loaded. If you see undefined, the build didn't pick up your changes—verify Git committed netlify.toml.

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Still broken? Check these too

1. [Syntax error in netlify.toml](/?guide=toml-validation) — Invalid TOML prevents entire config from loading. Use a TOML validator or npm install -D toml to test parsing.

2. Secrets vs. environment variables — Sensitive values (API keys, tokens) should be set via Netlify UI *and* added to [context.production] to prevent exposure in build logs. Never commit secrets to Git or netlify.toml.

3. [Function bundling config mismatch](/?guide=netlify-bundler) — If using a custom bundler (esbuild, webpack), ensure it preserves process.env references and doesn't tree-shake them out as "unused".

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Official Resources

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Quick Checklist

Found a different variation? Drop it in the comments.