Durham-based Windsor Circle, a fast-growing startup that develops software designed to improve customer retention, has landed $5.25 million new funding. Comcast Ventures led the round along with Triangle investors and AOL founder Steve Case.

IDEA Fund Partners and Triangle Angel Partners, which had invested previously in Windsor Circle, also participated in the Series B round of funding.

Case agreed to invest in Windsor Circle after the company won a Google startup showcase in Silicon Valley.

“The modern marketer needs both data science and automation in order to personalize content and delight the consumer. We are constantly working to improve and augment our retention marketing technology and software in order to help retailers keep their customers” said Windsor Circle CEO Matt Williamson. “This new funding both validates and enables our vision.”

Windsor Circle now has some 200 retail clients.

According to the company, Windsor Circle’s software increases revenue from repeat buyers by 20 percent.

The company recently relocated to additional space in Durham and now has 25 employees with several open positions.