Best USPS CASS-Certified Address Validation APIs
Address verification APIs with official postal certification (USPS CASS and equivalents) for accurate, mailable, standardized addresses.
Our pick: Lob Address Verification
Lob Address Verification is a REST API for validating, standardizing, and autocompleting postal addresses, covering all US territories through USPS CASS Cycle O certification and 240+ international territories. It targets developers and businesses needing real-time checkout validation, bulk mailing list hygiene, or CRM data cleansing. Pricing starts at $0.025 per 1,000 lookups with a free tier of 300 live US verifications per month and unlimited sandbox requests, plus enterprise plans via sales. The API ships official SDKs for eight languages and holds SOC 2 Type II, HIPAA, GDPR, and ISO 27001 certifications.
Best for: Prototypes and side projects - free to start, no sales call; Regulated or enterprise workloads - compliance attestations and an enterprise plan; Teams needing broad API coverage out of the box.
The catch: The cheapest US verification ($0.025 per 1,000) and very developer-friendly, but autocomplete is US-only and international coverage is thinner than the global data vendors.
Best for…
- Best overall
- Lob Address Verification
- Best free pick
- Lob Address Verification
- Best for enterprise
- Lob Address Verification
- Cheapest to start
- PostGrid Address Verification
- Best for agents
- Loqate Address Verification
- Broadest surface
- Service Objects DOTS Address Validation
Ranked (9)
#1 Lob Address Verification
74 / 100- Best overall
- Best free pick
- Best for enterprise
Lob Address Verification is a REST API for validating, standardizing, and autocompleting postal addresses, covering all US territories through USPS CASS Cycle O certification and 240+ international territories. It targets developers and businesses needing real-time checkout validation, bulk mailing list hygiene, or CRM data cleansing. Pricing starts at $0.025 per 1,000 lookups with a free tier of 300 live US verifications per month and unlimited sandbox requests, plus enterprise plans via sales. The API ships official SDKs for eight languages and holds SOC 2 Type II, HIPAA, GDPR, and ISO 27001 certifications.
PricingHybrid · from $0.03 1,000 lookups · free tier ✓TrustSOC 2 Type II · HIPAA · GDPR · ISO 27001DoesUsed byCurrent, CareWell, BlueChip FinancialThe catchThe cheapest US verification ($0.025 per 1,000) and very developer-friendly, but autocomplete is US-only and international coverage is thinner than the global data vendors.#2 Loqate Address Verification
75 / 100- Best for agents
Loqate Address Verification is a REST API for validating, capturing, cleansing, and geocoding postal addresses across 250 countries and territories, with postal certification for the US (USPS CASS), Australia (AMAS), Canada (SERP), and the UK (Royal Mail PAF). It suits e-commerce checkout, customer onboarding, KYC workflows, and mailing list hygiene. Pricing is credit-based with published rates (US address capture at 4.7 cents each, starting at $100), a 45-day free trial with no credit card required, and enterprise plans available. The platform holds SOC 2 Type 2, ISO 27001, PCI DSS, and GDPR certifications, and counts IBM, Oracle, Sephora, and JetBlue among its customers.
PricingUsage · from $100 credit bundle (e.g. $100 buys credits; US address capture at 4.7¢ each) · free tier ✗TrustSOC 2 Type II · GDPR · ISO 27001 · PCI DSSDoesUsed byIBM, Oracle, Fanatics, SephoraThe catchThe broadest global coverage (250 countries, CASS/SERP/PAF/AMAS certified), but pricing is credit-bundle based and it carries more enterprise setup than the dev-first pure-plays.#3 PostGrid Address Verification
68 / 100- Cheapest to start
PostGrid Address Verification is a REST API that autocompletes, validates, standardizes, and geocodes addresses across 250+ countries, with postal authority certifications for the US (USPS CASS), Canada (Canada Post SERP), UK (Royal Mail PAF), and Australia (Australia Post AMAS). It suits checkout flows, CRM hygiene, mailing list cleansing, and bulk batch processing up to one million addresses per API call. Pricing starts at $18 per month with 500 free trial lookups and self-serve signup, though international coverage beyond the US and Canada requires a separate higher-tier product. The service holds SOC 2 Type II, HIPAA, GDPR, and PCI DSS compliance, and offers SDKs for Node.js/TypeScript and Python.
PricingHybrid · from $18 month · free tier ✗TrustSOC 2 Type II · HIPAA · GDPR · PCI DSSDoesUsed byMutual of Omaha, Cognizant, Oura, Leon'sAvoid ifYou want to try it free before paying#4 Smarty (US & International Address Verification)
65 / 100Smarty is a REST API for US and international address verification, offering USPS CASS-certified validation with DPV, ZIP+4, and geocoding for US addresses, plus street-level verification across 249 countries. It suits ecommerce checkout, mailing list hygiene, logistics, KYC onboarding, and healthcare workflows. Plans start at $50/month with a 1,000-lookup trial, self-serve signup, and SDKs for nine languages. SOC 2 Type 2 certified and GDPR compliant; HIPAA compliance and BAAs require an Enterprise plan.
PricingSubscription · from $50 month · free tier ✗TrustSOC 2 Type II · HIPAA · GDPRDoesUsed byNASA, Uber, Chase Bank, Cox CommunicationsThe catchFast, accurate, and well-documented, but there is no recurring free tier (42-day trial only) and international verification is a separate, pricier product.#5 Service Objects DOTS Address Validation
47 / 100- Broadest surface
Service Objects DOTS Address Validation is a USPS CASS-certified REST API for validating, correcting, and standardizing postal addresses across the US, Canada, and 250-plus countries, used for e-commerce checkout, CRM hygiene, and fraud detection. A one-time 500-transaction trial key is available without a sales call, but production pricing requires contacting sales. The service holds SOC 2 Type 1 and PCI DSS certifications, complies with GDPR, and publishes an SLA. SDKs are available for .NET, Python, and Node.js, and a multi-language MCP server is also offered.
PricingSales-led · free tier ✗TrustSOC 2 Type I · GDPR · PCI DSSDoesUsed byAmazon, Microsoft, Mastercard, American ExpressAvoid ifYou need transparent pricing up front#6 Precisely Verify (Address Verification)
55 / 100Precisely Verify is an enterprise address validation API from Precisely that covers 250+ countries, with USPS CASS Cycle O, Canada Post SERP, and Royal Mail PAF certifications alongside FedRAMP authorization for government use. It handles address standardization, geocoding, autocomplete, and bulk geo-addressing via a REST API with OAuth2 auth and SDKs for Python, Java, Node.js, C#, Android, and iOS. Pricing is not published and requires a custom quote, though a one-time 30-day free trial with 2,500 credits is available without a credit card. The platform holds SOC 2 Type II, HIPAA, GDPR, and ISO 27001 compliance, making it suited to regulated industries and high-volume enterprise data pipelines.
PricingSales-led · free tier ✗TrustSOC 2 Type II · HIPAA · GDPR · ISO 27001DoesUsed byWillis RE, Poste Maroc, New Zealand Superannuation Fund, BelfiusAvoid ifYou need transparent pricing up front#7 Google Address Validation API
74 / 100Google Address Validation API validates and corrects postal addresses using Google Maps Places data, covering 40+ countries with USPS CASS certification for US and Puerto Rico addresses. It targets e-commerce checkout flows, financial services onboarding, and batch data quality use cases. Pricing starts at $17 per 1,000 requests with a free tier of 5,000 requests per month, and enterprise plans are available without a required sales call. The API is REST-based with SDK support for Java, Go, Node.js, Python, and .NET, and holds SOC 2 Type II, ISO 27001, and GDPR compliance.
PricingHybrid · from $17 1,000 requests · free tier ✓TrustSOC 2 Type II · GDPR · ISO 27001DoesThe catchBacked by Google Maps data and expanding, but results generally may not be cached or stored, and coverage outside the US is still a limited country list.#8 Experian Address Validation
33 / 100Experian Address Validation is a REST API for real-time and batch address validation, formatting, and enrichment across 245 countries and territories, with postal authority certifications for the US (USPS CASS), Canada (Canada Post SERP), UK (Royal Mail PAF), and Australia (Australia Post AMAS). It supports autocomplete, typedown, geocode append, and bulk cleansing via API key auth, with official SDKs for TypeScript, Java, and C#. Pricing is not published and requires a sales contact for production licenses, though a self-serve 14-day trial provides 2,000 validations for AU, CA, NZ, and USA. The service is ISO 27001 certified, carries a published SLA, and operates at a hard cap of 150 requests per minute.
PricingSales-led · free tier ✗TrustISO 27001DoesUsed byIKEA, Overstock.com, GS1 Australia, The Vitamin ShoppeAvoid ifYou need transparent pricing up front#9 Byteplant Address Validator
46 / 100Byteplant Address Validator is a REST API for real-time and bulk postal address verification, standardization, and geocoding, covering 240-plus countries and territories with USPS CASS certification for the United States. It targets e-commerce, logistics, and CRM teams looking to reduce failed deliveries and keep mailing lists clean. Plans start at $16 via self-serve credit bundles with a 100-validation free trial (no credit card required), while enterprise volumes above 100,000 addresses per year require a sales contact. Credits are region-tiered, geocoding is an add-on, and the service is GDPR compliant with personally identifiable data deleted within 14 days.
PricingSubscription · free tier ✗TrustGDPRDoesUsed byAlibaba, Toyota, Sonova, EWEAvoid ifYou need transparent pricing up front