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

Netlify Functions can't access env vars because they're defined in UI but not deployed to function runtime. Solution: add vars to netlify.toml [functions] context.

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

TL;DR

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Real Console Error Messages

``` 1. undefined is not an object (evaluating 'process.env.API_KEY') at Object.<anonymous> (.netlify/functions/api:1:200)

2. Error: process.env.DATABASE_URL is undefined at connectDB (/var/task/functions/db.js:5:15) at Runtime.handler (/var/task/functions/db.js:12:3)

3. TypeError: Cannot read property 'STRIPE_SECRET' of undefined at module.exports (.netlify/functions/payment.js:3:8)

4. ConfigError: Missing required env var: JWT_SECRET for function 'auth'

5. ReferenceError: process is not defined (when using Node 18+ runtime without proper bundling) ```

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Broken Code vs Fixed Code

Issue 1: Env vars only in Netlify UI

❌ BROKEN: ```javascript // .netlify/functions/api.js exports.handler = async (event) => { const apiKey = process.env.API_KEY; // undefined! const response = await fetch('https://api.example.com', { headers: { Authorization: Bearer ${apiKey} } }); return { statusCode: 200, body: JSON.stringify(response) }; }; ```

✅ FIXED: ```toml

netlify.toml

OR for development + production: ```toml [functions] environment = { API_KEY = "$API_KEY" }

[context.production] [context.production.functions] environment = { API_KEY = "$PROD_API_KEY" } ```

Then keep secrets in Netlify UI (Site settings → Build & deploy → Environment).

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Issue 2: Missing redeploy after adding env vars in UI

❌ BROKEN: 1. Add API_KEY in Netlify UI 2. Redeploy only via git push 3. process.env.API_KEY still undefined

✅ FIXED: ```bash

Option A: Trigger rebuild via Netlify UI

Go to: Deploys tab → Trigger deploy → Deploy site

Option B: Clear cache and redeploy

Deploys → Deploy settings → Clear cache and deploy site

Option C: Use Netlify CLI

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Issue 3: Functions context mismatch

❌ BROKEN: ```javascript // Tries to read vars before function handler const API_KEY = process.env.API_KEY;

exports.handler = async (event) => { // API_KEY is undefined here return { statusCode: 200, body: API_KEY }; }; ```

✅ FIXED: ```javascript // Read inside handler function exports.handler = async (event) => { const API_KEY = process.env.API_KEY; // Now defined! return { statusCode: 200, body: JSON.stringify({ key: API_KEY }) }; }; ```

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Why This Happens

Netlify Functions run in an isolated Lambda-like environment. Environment variables set in the Netlify UI are stored separately from your function code and only injected at runtime. If you:

The functions won't see them.

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Still broken? Check these too

1. Node version mismatch: If using Node 18+ and getting ReferenceError: process is not defined, your function may have incorrect bundling. Verify runtime = "nodejs18.x" in netlify.toml and rebuild.

2. Local vs production discrepancy: .env files work locally but not in production. Always test with netlify functions:invoke or check actual deploy logs (Site settings → Deploys → View deploy log).

3. Stale cache in browser: Functions cached a bad result. Clear your browser cache, or add Cache-Control: no-cache header and wait 10 minutes for edge cache to expire. Also see [Netlify cache troubleshooting guide](/?guide=cache-busting).

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Verification Checklist

```javascript // Add this to your function to debug exports.handler = async (event) => { console.log('Available env vars:', Object.keys(process.env).filter(k => k.includes('API'))); console.log('API_KEY value:', process.env.API_KEY ? '[SET]' : '[MISSING]'); return { statusCode: 200 }; }; // Check in: Netlify UI → Functions → Logs (or CloudWatch) ```

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Related Issues

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Official Docs

[Netlify Environment Variables Documentation](https://docs.netlify.com/configure-builds/environment-variables/)

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Found a different variation? Drop it in the comments—env var issues have many flavors at 2am.