Lob.com vs US Street Address

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 Street API is a CASS-certified single/batch address validator: it corrects, standardizes, and appends ZIP+4, county, carrier route, and delivery-point-validation (DPV) data to a US postal address, flagging vacant, undeliverable, or CMRA (commercial mail receiving agency) addresses along the way. Requests can be sent as GET query parameters or as a JSON/XML batch of up to 100 addresses per POST, and responses are returned in the same format. It shares an account and API key with Smarty's other address-data products, including US Autocomplete and US Extract.