# Debugging Environment Variables

> Use the dev-tool app to inspect environment variables and validation errors.

*Canonical: https://makerkit.dev/docs/nextjs-drizzle/dev-tools/environment-variables*

---

The dev-tool app exposes an environment variables inspector at `http://localhost:3010/variables` when the dev-tool app is running.

{% img src="/assets/images/dev-tools-env-variables.webp" width="1000" height="600" alt="Environment variables dev tool" /%}

## What It Reads

For the web app, the tool inspects the `apps/web/.env*` files and shows effective values plus validation state.

## Extend the Tool

Add new variable definitions in:

```text
apps/dev-tool/app/variables/lib/env-variables-model.ts
```

Related implementation files:

- `apps/dev-tool/app/variables/lib/env-scanner.ts`
- `apps/dev-tool/app/variables/lib/server-actions.ts`

Use this tool when you need to confirm which value wins across `.env`, `.env.development`, and `.env.local`.