Lob.com vs US Autocomplete

Lob's US Address Verification API checks, standardizes, and CASS-certifies a US postal address in real time, returning delivery-point-validation flags, vacancy and building-type metadata, and a corrected/deliverable address in one JSON response. It's the same verification engine behind Lob's broader direct-mail automation platform (mail creation, printing, and USPS tracking), so a key created for one Lob product works across the rest. Authentication is a single API key sent as the HTTP Basic Auth username, with separate test and live keys so integrations can be built and tested before any usage is billed.

Smarty's US Autocomplete Pro API suggests valid, USPS-backed US addresses as a user types, turning a single free-form "search" string into a ranked list of deliverable candidates for checkout and signup forms, with optional city/state/ZIP filters to narrow the results. A separate "selected" parameter expands a chosen address into its individual secondary units (apartments, suites) when it resolves to more than one. It's part of Smarty's wider address-data platform, so one account and key also unlock the sibling US Street Address and US Extract APIs.