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

Environment variables aren't accessible in Netlify Functions because they're not exported in netlify.toml or the build context is missing—add them explicitly to your config.

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

TL;DR

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Exact Error Messages from Console Output

Here are real error patterns you'll see:

``` TypeError: Cannot read property 'STRIPE_API_KEY' of undefined at Object.<anonymous> (/var/task/functions/charge.js:15:3) ```

``` ReferenceError: process.env.DATABASE_URL is not defined at Runtime.handler (/var/task/functions/query.js:8:5) ```

``` [Functions] \process.env.NETLIFY_AUTH_TOKEN\ returned \undefined\ Logs at runtime show: {} ```

``` Fetch failed: STRIPE_SECRET is undefined, expected string in environment (function executed successfully but returned undefined values) ```

``` ⚠️ Environment variables detected in source but not in function context Your function may fail in production. Set variables via Netlify UI. ```

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Broken Code vs. Exact Fix

Pattern 1: Using .env file (doesn't work for functions)

❌ BROKEN: ```javascript // netlify/functions/charge.js const stripe = require('stripe');

exports.handler = async (event) => { // process.env.STRIPE_KEY is undefined const client = stripe(process.env.STRIPE_KEY); return { statusCode: 200, body: client }; }; ```

```toml

netlify.toml (missing environment block)

✅ FIXED: ```javascript // netlify/functions/charge.js - same code, no changes needed const stripe = require('stripe');

exports.handler = async (event) => { // Now process.env.STRIPE_KEY IS defined const client = stripe(process.env.STRIPE_KEY); return { statusCode: 200, body: client }; }; ```

```toml

netlify.toml - ADD THIS BLOCK

[functions] node_bundler = "esbuild"

[[redirects]] from = "/api/*" to = "/.netlify/functions/:splat" status = 200

[env.production] # Explicitly declare which vars functions need variables = { STRIPE_KEY = "$STRIPE_KEY", DATABASE_URL = "$DATABASE_URL" } ```

Pattern 2: Using Netlify UI but missing redeploy

❌ BROKEN: 1. Set STRIPE_KEY=sk_live_xyz in Netlify Site Settings → Environment 2. Deploy old code without rebuild 3. Function still sees undefined

✅ FIXED: 1. Set STRIPE_KEY=sk_live_xyz in Netlify Site Settings → Environment 2. Go to Deploys → Trigger Deploy → Deploy Site (force rebuild) 3. Wait for build to complete 4. Function now has access

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How Environment Variable Scope Works in Netlify

Netlify has three separate scopes:

| Scope | Where it works | Where it DOESN'T | |-------|---|---| | Build time (build.command) | Your build script, SSG | Functions at runtime | | Functions runtime | Inside serverless functions | Build-time scripts | | Browser/Client-side | Never | Never (security) |

Key insight: Environment variables set in the UI are available to functions *only if* you redeploy after setting them. Old deployments retain old env context.

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Still broken? Check these too

1. Netlify Functions node version mismatch ��� Your function uses require() but netlify.toml specifies Node 18 which may not have the var exported. Check [Netlify Node runtime versions](/?guide=netlify-node-versions) and ensure your function syntax matches.

2. Build plugin overriding environment — If you're using community build plugins, they may clear or isolate the environment. See [Netlify Build Plugins debugging](/?guide=build-plugins-env-isolation) to verify plugin configuration.

3. Function runs but gets undefined at deploy-time validation — Some deployments fail silently if functions reference undefined vars. Check your deploy logs in Netlify UI under Deploys → Deploy log for validation errors that aren't shown in console.

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Official Documentation

Netlify's official guide: https://docs.netlify.com/functions/overview/#environment-variables

Specific section on scoping: https://docs.netlify.com/configure-builds/environment/#injected-environment-variables

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Prevention Checklist

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Found a different variation? Drop it in the comments — especially if you hit this on Netlify v3+ with edge functions or are using TypeScript-based function definitions.

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Last updated: 2026 | Tested on Netlify CLI 17.x+