PostgreSQL Error 28P01 - Invalid Password

What It Means

PostgreSQL error code 28P01 (invalid_password) means authentication failed because the password provided for the user is incorrect. The error message typically reads: password authentication failed for user "username".

This is different from connection errors — the client successfully reached the PostgreSQL server, but the credentials were rejected.

Common Causes

• Wrong password for the database user
• User does not exist in PostgreSQL
• Password was recently changed
• Environment variable has extra whitespace or quotes in the password
• Connecting to the wrong PostgreSQL instance
• pg_hba.conf authentication method mismatch
• Password contains special characters not properly escaped

How to Fix

Reset the user password

# Connect as the postgres superuser
sudo -u postgres psql

# Change the password
ALTER USER myapp WITH PASSWORD 'new_secure_password';

# Or create the user if it doesn't exist
CREATE USER myapp WITH PASSWORD 'new_secure_password';
GRANT ALL PRIVILEGES ON DATABASE mydb TO myapp;

Check pg_hba.conf

# Find pg_hba.conf location
sudo -u postgres psql -c "SHOW hba_file;"

# Edit pg_hba.conf
sudo nano /etc/postgresql/16/main/pg_hba.conf

# pg_hba.conf - common configurations
# TYPE  DATABASE  USER  ADDRESS       METHOD
local   all       all                 peer      # Local connections use OS user
host    all       all   127.0.0.1/32  md5       # Require password for TCP
host    all       all   0.0.0.0/0     scram-sha-256  # Remote with password

# After editing, reload PostgreSQL
# sudo systemctl reload postgresql

Verify connection details

# Test connection
psql -h localhost -U myapp -d mydb -W

# Check if the user exists
sudo -u postgres psql -c "SELECT usename FROM pg_user;"

# Check if the user can connect to the database
sudo -u postgres psql -c "SELECT datname, has_database_privilege('myapp', datname, 'CONNECT') FROM pg_database;"

Fix environment variables

# Check for whitespace or quote issues
echo "'$DATABASE_PASSWORD'"  # Look for extra characters

# Set properly in .env
DATABASE_URL=postgresql://myapp:password@localhost:5432/mydb

# Don't use quotes around values in .env files (depends on the parser)
DB_PASSWORD=my_secure_password    # Good
DB_PASSWORD="my_secure_password"  # May include quotes literally

Application configuration

// Node.js with pg
const { Pool } = require('pg');

const pool = new Pool({
  host: 'localhost',
  port: 5432,
  database: 'mydb',
  user: 'myapp',
  password: process.env.DB_PASSWORD,  // Verify this is set correctly
});

// Or use a connection string
const pool = new Pool({
  connectionString: process.env.DATABASE_URL
});

// Test the connection
pool.query('SELECT 1')
  .then(() => console.log('Connected'))
  .catch(err => console.error('Connection failed:', err.message));

# Python with psycopg2
import psycopg2

try:
    conn = psycopg2.connect(
        host='localhost',
        port=5432,
        dbname='mydb',
        user='myapp',
        password='secure_password'
    )
except psycopg2.OperationalError as e:
    if '28P01' in str(e):
        print("Invalid password. Check your credentials.")
    raise

Docker PostgreSQL

# Docker Compose
services:
  db:
    image: postgres:16
    environment:
      POSTGRES_USER: myapp
      POSTGRES_PASSWORD: secure_password
      POSTGRES_DB: mydb
    ports:
      - "5432:5432"

Related Errors

• PostgreSQL 42P01 - Undefined table: Authenticated but the table doesn’t exist.
• MySQL 1045 - Access denied: The MySQL equivalent of authentication failure.