Openads, the developer of the free, open source ad server now used by more than 30,000 publishers worldwide, announced the completion of its Series B financing. The $15.5 million investment was led by Accel Partners, with participation from existing investors Index Ventures, First Round Capital, Mangrove Capital Partners and O’Reilly AlphaTech Ventures. The company will use the funds to accelerate product development and expand its team to support its large publisher community, which is now using Openads to deliver billions of ads daily in over 100 countries around the world.

Openads lets publishers take control of their advertising, providing simple, powerful and independent tools to schedule, manage and track online campaigns. The software also supports a broad range of ad formats and advertiser types (including direct advertisers and ad networks such as Google AdSense, Yahoo! and Advertising.com). The new hosted version will make it even easier and faster for publishers to make more money from online advertising by eliminating the need to run the software on their own servers.

The rapid growth of the global online advertising market requires the adoption of next generation infrastructure and services for publishers and advertisers alike,” said Andrew Braccia of Accel Partners. “Openads’ open source heritage and deep global publisher footprint make it uniquely positioned to play a pivotal role in the evolution of the digital media landscape.”

Openads helps publishers make more money from online advertising. The company provides for free its sophisticated, open source ad serving software, giving website owners everything they need to schedule, manage and track their online inventory. Based in London, England, Openads is backed by leading investors including Accel Partners and Index Ventures.