USPS Web Tools retired.
Your address + rates layer is ready.

# Validate an address (free tier)
curl "https://api.revaddress.com/api/address/validate\
?streetAddress=1600+Pennsylvania+Ave&city=Washington&state=DC&ZIPCode=20500" \

# 200 OK — 42ms
{
  "streetAddress": "1600 PENNSYLVANIA AVE NW",
  "ZIPCode": "20500",
  "DPVConfirmation": "Y"
}

# Install
pip install usps-v3

# Validate an address
from usps_v3 import Client

client = Client("your_api_key")
result = client.addresses.validate(
    street="1600 Pennsylvania Ave",
    city="Washington",
    state="DC",
    zip_code="20500"
)

print(result.zip)  # "20500-0005"
print(result.dpv)  # "Y" (deliverable)

// Install: npm install usps-v3
import { USPSClient } from 'usps-v3';

const client = new USPSClient("your_api_key");
const result = await client.addresses.validate({
  street: "1600 Pennsylvania Ave",
  city: "Washington",
  state: "DC",
  zipCode: "20500"
});

console.log(result.zip);  // "20500-0005"
console.log(result.dpv);  // "Y" (deliverable)

// Install: composer require revaddress/usps-v3-php
use RevAddress\USPSv3\Client;

$usps = new Client('your-client-id', 'your-client-secret');
$result = $usps->validateAddress([
    'streetAddress' => '1600 Pennsylvania Ave NW',
    'city'          => 'Washington',
    'state'         => 'DC',
    'ZIPCode'       => '20500',
]);

echo $result['address']['ZIPCode'];  // "20500-0005"
echo $result['address']['DPVConfirmation'];  // "Y"