The header bidding from Appnexus has now more than 70 adapters, that includes ad networks and ad exchanges, including video (in stream and outstream) and native. Matt Jacobson, Product Manager at AppNexus, said here that he is excited with the growth of header bidding, specially with the new formats like video and native, and also the server to server integrations. Matt talked also about Appnexus being open to develop new features for the publishers. He gave the example of the randomization of the order in which bidders are contacted.
Chris Parker, Chief Marketing Technologist of WhatIsMyIPAddress.com, tested some adapters and the top 3 best performing were AppNexus, Index Exchange and Sovrn. On OpenX, and in Pubmatic, he discovered that there is a minimum monthly volume requirement.
See here the public list of partners working with Prebid: AppNexus, OpenX, PubMatic, Rubicon, Yieldbot, AOL, Index Exchange, Sovrn, PulsePoint, TripleLift, SpringServe, Adform, bRealTime, Beachfront, NginAd, Brightcom, Adequant, Sonobi, Aardvark, WideOrbit, Krux Link, AdMedia, JCM, SmartyAds, Meme Global, Underdog Media, Centro, Conversant, Adblade, Piximedia, GetIntent, HIRO Media, Roxot, Komoona, RhythmOne, FeatureForward, Huddled Masses, DistrictmDMX, GumGum, Vertoz, Smart AdServer, AdButler, Sharethrough,Mantis Ad Network, AdMixer, Twenga, Lifestreet, Vertamedia, StickyAdsTV, 152Media, Matomy, Fidelity Media, ThoughtLeadr, TapSense, Atomx, Bidfluence, Trion, Innity.