500px

500px is a photography platform combining a community for sharing and showcasing images with a marketplace where photographers can license their work to buyers. Members browse, favorite and comment on photos, follow other photographers and build a portfolio, while the licensing side connects photographers with businesses and individuals looking for stock imagery for their own projects.

Its ads.txt file lists 174 ad systems, made up of 69 direct relationships and 148 resellers. Sales houses named include BuySellAds, Publift, NoBid, Krush Media and 33Across, among others placing ad spots on the site.