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

Env vars undefined in Netlify Functions? Missing netlify.toml config or runtime mismatch. Add [[functions]] block with node_bundler setting.

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

TL;DR

---

Real Console Error Messages

``` Error: process.env.DATABASE_URL is undefined at Object.<anonymous> (/var/task/functions/api.js:12:5) at Module._load (node:internal/modules/require_cache:js:165:29) ```

``` ReferenceError: Cannot read property 'DATABASE_URL' of undefined at handler (/var/task/src/functions/query.js:8:23) ```

``` [Functions] Error during execution: unable to resolve "process.env.API_KEY" ```

``` Warning: dotenv did not load in production Your environment variables are empty {} ```

``` TypeError: Cannot destructure property 'API_SECRET' of 'undefined' at Object.<anonymous> (functions/auth.js:1:1) ```

---

The Problem Explained

Netlify Functions in production don't automatically inject environment variables the way your local dev server does. The issue stems from one of three causes:

1. Missing netlify.toml configuration – Functions aren't told where to find env vars 2. Node bundler incompatibility – Using webpack instead of esbuild prevents proper variable tree-shaking 3. Runtime environment mismatch – Local Node 16 vs. Netlify's Node 18/20 handle dotenv differently

---

Broken vs. Fixed Code

Scenario 1: No netlify.toml Configuration

BROKEN: ```toml

netlify.toml (missing function config)

FIXED: ```toml

netlify.toml

[[functions]] node_bundler = "esbuild" environment = { DATABASE_URL = "$DATABASE_URL", API_KEY = "$API_KEY" } ```

Scenario 2: Incorrect Env Var Access in Function

BROKEN: ```javascript // netlify/functions/api.js const { DATABASE_URL } = process.env;

exports.handler = async (event) => { const conn = await connect(DATABASE_URL); // undefined! return { statusCode: 500 }; }; ```

FIXED: ```javascript // netlify/functions/api.js exports.handler = async (event) => { const DATABASE_URL = process.env.DATABASE_URL; if (!DATABASE_URL) { return { statusCode: 500, body: JSON.stringify({ error: "DATABASE_URL not set" }) }; } const conn = await connect(DATABASE_URL); return { statusCode: 200 }; }; ```

Scenario 3: Netlify UI Environment Variables Not Set

BROKEN: ```bash

Netlify Dashboard shows no env vars in Site Settings > Build & Deploy > Environment

Or vars are named differently than in code

FIXED: ```bash

In Netlify Dashboard:

1. Go to Site Settings → Build & Deploy → Environment

2. Click "Edit variables"

3. Add: DATABASE_URL = "your_actual_db_url"

4. Add: API_KEY = "your_actual_key"

5. Redeploy the site (or trigger new deployment)

---

Step-by-Step Fix

1. Check netlify.toml exists in repo root: ```bash cat netlify.toml ```

2. Add or update the functions section: ```toml [[functions]] node_bundler = "esbuild" ```

3. Verify env vars in Netlify Dashboard: - Site Settings → Build & Deploy → Environment Variables - Ensure all vars referenced in code are listed

4. Access safely in code: ```javascript const key = process.env.API_KEY || "fallback_value"; ```

5. Redeploy: ```bash git push origin main ```

6. Check deployment logs (Netlify Dashboard → Deploys → latest) for errors.

---

Still broken? Check these too

Issue #1: Function not triggering at all

Issue #2: Env vars work locally but not in production

Issue #3: Timeout or permission denied errors

---

Version Note

---

Official Resources

---

Found a different variation? Drop it in the comments.