List of online advertising DSPs from around the Web. The term DSP means "demand-side platform." This refers to a service that handles bids and purchasing for online ads on behalf of another company, typically in an auction-based system. (In other words, the DSP is bidding for online ad space on behalf of an advertiser or marketer.) The DSP thus is an impartial third-party service that can work with a variety of companies and clients on one side, and with a variety of ad networks and publishers on the other side. Several companies, including Yahoo and Google, operate their own DSPs, while some DSPs operate independently.What are the best DSP companies? Some of the largest DSPs listed here include InviteMedia (which is owned by Google subsidiary DoubleClick) and AppNexus. The names of all top demand side platform companies can be found here on this top advertiing DSP list.