eBay vs Flipkart Marketplace

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.

Flipkart's Marketplace Seller API issues OAuth2 bearer tokens through either a client-credentials or an authorization-code grant, for self-access and third-party seller applications respectively. Its own documentation explicitly requires HTTPS and states plain HTTP requests are rejected, with tokens typically valid for around 60 days before they must be renewed.