This is get-all-clients

import { sql } from '@vercel/postgres';
import { NextResponse } from 'next/server';

export async function GET() {
    try {
        const result = await sql`SELECT * FROM clients;`
        return NextResponse.json({ rows: result.rows }, { status: 200 });
    } catch (err) {
        console.error(err);
        return NextResponse.json({ err }, { status: 500 });
    }
}

Next is also correctly using env variables. Forgot to mention that .env is on the root folder

Vercel setups the env variables

They doesn't seem to be reachable inside the app

My last hope was to use

import { config } from 'dotenv';
config();

but didn't work

What do you mean, it only supplies the variables on their side. Did you copy the variables to your local .env file, since you are testing it on localhost

To my .env file? Yes

Now it's called .env, cause .env.development and .env.development.local weren't working anyways

I'm pretty sure those are the uploaded env variables

On my proyect's settings tab

That's right, you probally linked the database to the project, but that doesn't have to do anything with testing on localhost. Did you check if POSTGRES_URL is in your local .env file or you missed to copy it. Normally you dont need anything custom to load .env file

That was the problem. Enviroment file is supplied but Its values cannot be read from the app

"undefined" for all variables

That's why i've tried this

Does it work on vercel?

Where do I test it on vercel? Env variables work when fetching api's urls from the browser

doesn't make any sense to me