Postman Echo vs US Autocomplete

Postman Echo is a keyless sandbox that mirrors whatever you send it back as JSON — headers, query args, form body, cookies, and basic/digest auth attempts — across GET, POST, PUT, DELETE, and PATCH endpoints, plus helpers for testing redirects, delays, streaming, and gzip/deflate encoding. It's built and maintained by the Postman team as the reference backend for their own client tutorials and public collections, so its request/response shapes double as worked examples. There's no signup or key: every route is open, making it a quick target for scripting HTTP-client tests without standing up your own server.

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.