CowboyIn the fast-moving world of advertising, online is the Wild Wild West, with brands, ad networks, startups, and investors eager to stake their claim.

The biggest, baddest ad tech company to roll into town today is AppNexus, which announced raising $75 million in its fourth round of funding.

AppNexus provides a customizable ad tech platform that businesses can use to build a differentiated ad network, trading desk, or custom exchange. The company has a large database of ad buyers and sellers and a real-time bidding exchange. Customers have access to global network as well as tools to optimize their campaigns and manage their ad inventory and the data it generates.

The platform is designed to be as flexible and customizable as possible to suit clients of all needs and sizes. In the past 12 months, AppNexus has managed approximately $700 million of advertising spend, almost tripled revenues, processed a peak of one million requests per second, and quintupled delivery to over 13 billion ads served to websites each day.

These numbers came in a statement issued this morning regarding the investment, which was led by Technology Crossover Ventures. Venrock and Tribeca Venture Partner also participated in this round. The money will be used to “create the next generation of innovations that will transform online advertising.” It brings AppNexus’ total funding to $140.5 million. Previous investors include an elite group of First Round Capital, Marc Andresseen and Ben Horowtiz, Ron Conway, and Khosla Ventures.

AppNexus is based in New York City. Read the press release.