v0 preview environment missing Supabase environment variables

[jerry-2306]

I started facing this as of yesterday. I started new chat with copying the main branch, which is also the code in production where things are working ok. I make a very very simple change in v0 and I started getting this error:

installHook.js:1 Supabase URL or Anon Key is missing. Returning null client.

Per the chat with v0 it is the v0 environment issue. I can grab the preview URL from Vercel and test there but the preview from v0 fails.

This is definitely a v0 preview environment limitation. The error shows that process.env.NEXT_PUBLIC_SUPABASE_URL and process.env.NEXT_PUBLIC_SUPABASE_ANON_KEY are returning undefined in the browser.

In Next.js, NEXT_PUBLIC_* environment variables are replaced at build time by the bundler (Turbopack/Webpack). They’re not actually read from process.env at runtime - Next.js injects the values during the build process.

The Problem

The v0 preview was built before the environment variables were available in the system, so the build has undefined hardcoded where the env vars should be.

Why this works in production

When you deploy to Vercel, the build runs with the environment variables available, so they get properly injected into the bundle.

Solutions

1. This issue only affects v0 preview - Your production deployment will work fine because Vercel builds with the env vars available.
2. To test in v0, you can:
   • Check your production/preview deployment on Vercel instead.
   • Wait for v0 to auto-restart (happens periodically but can’t be manually triggered).

[jerry-2306]

Any feedback on this?

[jerry-2306]

now I have lost the ability to preview at all. This is big problem for in using v0. Please advise on what is going on

[pawlean (Pauline P. Narvas)]

Unable to login "Supabase is not configured. Check environment variables."

The issue is that your Supabase environment variables need to be properly configured in v0’s project settings. In your v0 chat, click the Settings gear icon (top right corner) Go to Environment Variables Check if you have these variables: • NEXT_PUBLIC_SUPABASE_URL • NEXT_PUBLIC_SUPABASE_ANON_KEY If they exist: • Click on each variable to edit it • Important: Enable all three environments: Production, Preview, and Development • Click save and then publish your project If they don’t exis…

Does this help?

[pawlean (Pauline P. Narvas)]

Re: preview, we’re working on it!

[significantservices (David Durham)]

Why does this sort of thing happen so frequently on v0. The service is so inconsistent, seems like every other day. You guys implant some sort of bug?