US Autocomplete vs VATlayer

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.

vatlayer checks whether an EU VAT registration number is currently valid and, where the member state's VIES service exposes it, returns the registered company name and address alongside real-time and historical VAT/EU-VAT rate lookups by country. It's one of the apilayer family of JSON micro-APIs, sharing that group's account and billing platform. Requests are plain HTTPS GET calls authenticated with an `access_key` query parameter — no headers or OAuth handshake required.