P1001: Can't reach database server at `YOUR_HOST`:`5432`

TL;DR: Check the host and port in your connection string first, then whether the database is actually listening, then whether you are pointing at a pooler port by mistake. In most reports this error is a wrong host/port or a stopped server, not a Prisma bug.

Error: P1001: Can't reach database server at `YOUR_HOST`:`5432`

Steps

1. Verify the host and port are what you think:

   node -e "const u=new URL(process.env.DATABASE_URL); console.log(u.hostname+':'+u.port)"

Expected: the host and port of your real database. A stale port (for example 5433 from an old setup) is the single most common cause.

1. Check the server is listening:

   nc -zv YOUR_HOST 5432

Expected: succeeded. If it fails, start the database (for example docker compose up -d db) and retry.

1. If you connect through Supabase / a pooler, use the matching port and mode: session-mode pooler on port 5432 for Prisma Client, transaction-mode pooler on 6543 only with ?pgbouncer=true. Mixing them produces P1001.

Expected: with the right port and mode, npx prisma db pull connects.

1. Re-run your app or npx prisma validate.

Expected: P1001 gone. If it becomes P1000, the host is reachable and the credentials are now the problem.

When to use

• The exact code is P1001 Can't reach database server
• The failure is immediate on connect, not after a timeout (that would be P2024)

When not to use

• P1000 (authentication failed): the server is reachable, your credentials are wrong
• P1003 (database does not exist): the server is reachable, the named database is missing

Compatibility

Prisma Client 4.x through 6.x. PostgreSQL, MySQL, SQL Server.

Variant phrasing: P1001 in Docker Compose where the host is the loopback address

Inside a container, the loopback address means the container itself. Use the service name (for example db) as the host instead.

Variant phrasing: P1001 right after changing providers or regions

Connection strings go stale on migration. Re-copy the current connection string from the provider dashboard.

Why it happens

P1001 means the TCP connection never opened: wrong host, wrong port, firewall, stopped server, or a pooler/direct mismatch. Prisma never got far enough to attempt authentication, which is why the fix is always in the network path or the server state.

Edge cases

• IPv6-only hosts: some resolvers return an IPv6 address the client cannot route; try the IPv4 address explicitly.
• sslmode or sslaccept params do not cause P1001; they surface later in the handshake.
• Cloud SQL / RDS proxy endpoints change on failover; re-resolve the hostname.