Theo's Typesafe Cult•17mo ago

api calls don't work in vercel

I'm trying to call my NextJS API: If I try to write const res = await fetch("/api/commands"); I get the error 'failed to parse URL' despite the API endpoint clearly existing and being accessible via http://localhost:3000/api/commands. To get around this, I declared a base URL variable so I could at least make it work in localhost and hopefully Vercel too (according to Vercel's docs they have a VERCEL_URL that points to the deployment's URL):

export const BASE_URL =
  process.env.NODE_ENV === 'development'
    ? 'http://localhost:3000'
    : `https://${process.env.VERCEL_URL}`;

export const BASE_URL =
  process.env.NODE_ENV === 'development'
    ? 'http://localhost:3000'
    : `https://${process.env.VERCEL_URL}`;

and then calling the api like so:

const res = await fetch(`${BASE_URL}/api/commands`);

const res = await fetch(`${BASE_URL}/api/commands`);

This works in localhost but not Vercel. How do you properly specify the base URL when calling your API handler?

2 Replies

rocawear•17mo ago

Have you looked from "Network" tab where it tries to get the data when deployed to vercel? I think you should do:

export const BASE_URL =
  process.env.VERCEL_URL
    ? 'https://${process.env.VERCEL_URL}'
    : `http://localhost:3000`;

export const BASE_URL =
  process.env.VERCEL_URL
    ? 'https://${process.env.VERCEL_URL}'
    : `http://localhost:3000`;

functionthatreturnsfalse•17mo ago

Ok, a few things were wrong. After digging a bit, it looks like the correct variable name is actually NEXT_PUBLIC_VERCEL_URL. Moreover, i dug into my api handler and found an unhandled case where i didn't send a response. I also converted my server component to a client component and fetched the data with a useEffect. ugly but works I'm not sure about my last solution, feels more like a bandaid, but at least it works.

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api calls don't work in vercel