# Preview branches on Vercel

Keep Vercel preview deployments off your production database.

Match each Vercel preview deployment to its Supabase preview branch, so every preview runs against the right database schema, Edge Functions, and other Supabase configuration.

Use this guide when you already get a Supabase preview branch for each pull request, and your frontend deploys a Vercel preview for each pull request too. Without this integration, those previews use the Supabase URL and keys set on your Vercel project, which usually point at your production project. A preview built to test a schema change then reads and writes production data.

If you don't have preview branches yet, start with [Branching](https://supabase.com/docs/guides/deployment/branching). To manage Supabase projects from your Vercel account instead, see [Vercel Marketplace](https://supabase.com/docs/guides/integrations/vercel-marketplace).

## Prerequisites

Before you connect Vercel, you need the following:

- [Branching](https://supabase.com/docs/guides/deployment/branching) set up on your Supabase project.
- Your Vercel project connected to its GitHub repository through the [Vercel GitHub integration](https://vercel.com/docs/deployments/git/vercel-for-github).

## Connect Vercel

To connect Vercel to your Supabase project:

1. On your organization's [**Integrations**](https://supabase.com/dashboard/org/_/integrations) page in the Supabase Dashboard, click **Install Vercel integration** and finish the installation in Vercel. You can also click **Deploy** in a Supabase example app's `README` file.
2. Click **Add new project connection**, then select your Supabase project and your Vercel project.

## After you connect

Supabase updates your Vercel project with the environment variables for each preview branch. It syncs them when a pull request opens, not when the branch is created. The variables are:

- **Postgres connection:** `POSTGRES_URL`, `POSTGRES_PRISMA_URL`, `POSTGRES_URL_NON_POOLING`, `POSTGRES_USER`, `POSTGRES_HOST`, `POSTGRES_PASSWORD`, and `POSTGRES_DATABASE`.
- **Supabase API:** `SUPABASE_URL`, `SUPABASE_PUBLISHABLE_KEY`, `SUPABASE_SECRET_KEY`, and `SUPABASE_JWT_SECRET`.
- **Public copies:** `NEXT_PUBLIC_SUPABASE_URL` and `NEXT_PUBLIC_SUPABASE_PUBLISHABLE_KEY`. To change the `NEXT_PUBLIC_` prefix, edit the project connection on the **Integrations** page.
- **Legacy API keys**, while they're enabled on your project: `SUPABASE_ANON_KEY`, `SUPABASE_SERVICE_ROLE_KEY`, and `NEXT_PUBLIC_SUPABASE_ANON_KEY`.

The integration depends on Vercel preview deployments, so Vercel can start a deployment before Supabase sets the variables. Supabase always redeploys the most recent deployment of the pull request to cover this.

To let users sign in on preview deployments, add a wildcard pattern for your Vercel preview URLs to the redirect allowlist. For the pattern, see [Vercel preview URLs](https://supabase.com/docs/guides/auth/redirect-urls#vercel-preview-urls).