Digi-Key vs eBay

Digi-Key's api.digikey.com gateway runs a genuine OAuth2 flow: its authorization endpoint rejects requests missing a client_id, and resource endpoints additionally require a client-specific header, ruling out simple API-key auth. Access to product, ordering, and barcode data is free with per-product rate limits, and CORS is explicitly configured, echoing the request Origin on both live calls and OPTIONS preflights.

eBay's REST platform — Browse, Sell, and related APIs — requires an OAuth2 client-credentials or authorization-code token, confirmed live by a standard invalid_client error from its token endpoint, and is built for server-side integration rather than in-browser calls. New developer accounts get a free daily call allowance with no published paid tier, and higher volume comes from an approval process rather than a fee.