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Validation

Address Verify CASS.
One API Key.

USPS CASS-certified US address verification powered by Smarty. DPV, ZIP+4, geocoding, and RDI classification.

Get Started FreeAlso available on RapidAPI →
Stateless API Processing — No request data stored

Try it now

Make a real API call — no setup required

curl -X POST "https://addressverifycass.vanmoose.cc/v1/verify" \
  -H "Authorization: Bearer vm_live_your_key" \
  -H "Content-Type: application/json" \
  -d '{}'

Run a request to see the response

Features

USPS CASS-Certified against the official postal database

Delivery Point Validation (DPV) — confirms real, deliverable mailbox

Address standardization with ZIP+4 and official USPS formatting

Geocoding with latitude/longitude coordinates

RDI classification — residential vs commercial

Bulk verification up to 1,000 addresses per request (plan-dependent)

Use Cases

E-commerce Checkout

Validate shipping addresses at checkout to prevent failed deliveries, reduce return costs, and improve customer satisfaction with real-time USPS verification.

Insurance & Financial Services

Verify policyholder and applicant addresses against the USPS database for compliance, risk assessment, and accurate correspondence delivery.

Direct Mail Campaigns

CASS-certify your mailing list before printing to qualify for USPS postage discounts and eliminate waste from undeliverable addresses.

CRM Data Cleansing

Bulk verify your contact database to standardize addresses, fill in ZIP+4, and flag vacant or non-deliverable records.

Pricing

Start free with 10/month. Scale up as you grow.

Free

10/month

Free
  • 10/month
  • 1/min
  • Hard limit
Get Started

Pro

200/month

$9.99/mo
  • 200/month
  • 5/min
  • Hard limit
Get Started
Best Value

Ultra

1.2k/month

$49.99/mo
  • 1.2k/month
  • 15/min
  • Hard limit
Get Started

Mega

6k/month

$199/mo
  • 6k/month
  • 30/min
  • Hard limit
Get Started

Frequently Asked Questions

CASS (Coding Accuracy Support System) is a USPS certification program. Our API uses a CASS-certified engine (Smarty) that validates addresses against the official USPS database, ensuring postal-grade accuracy.
Address Verify uses heuristic checks (format, ZIP patterns) without contacting USPS. AddressVerifyCASS performs a live USPS lookup with Delivery Point Validation, giving you definitive confirmation that an address is a real, deliverable mailbox.
DPV confirms that an address corresponds to an actual delivery point (mailbox) in the USPS system. A DPV match code of "Y" means confirmed deliverable, "S" means secondary info is missing (e.g., apartment number).
Yes. Starter plan supports 25 per request, Pro 100, Business 500, and Enterprise up to 1,000 addresses per request. Each address in a bulk request counts toward your monthly quota.

Start using Address Verify CASS API today

Free tier available. No credit card required.