Mercadolibre vs OLX Poland

Mercado Libre exposes a large REST surface across its Latin American marketplace sites, covering listings, orders, ads, and shipping. Public reference data like site categories is reachable without a token, but anything scoped to a seller account requires an OAuth2 access token obtained via an authorization-code or client-credentials grant. The API itself carries no direct usage fee — Mercado Libre monetizes through marketplace and payment commissions instead.

OLX Poland's Partner API lets approved integrators create and manage classified-ad listings and handle buyer/seller messaging programmatically. Access runs on an OAuth2 client-credentials flow, confirmed live by an invalid_client error from the real token endpoint, and the older v1 REST resource has been explicitly deprecated in favor of this OAuth-secured surface. Developer access comes through an application and approval process rather than a published self-serve fee.