Santa Monica’s Shift, a startup that helps marketers manage advertisements on social media platforms, sold Thursday for $50 million in cash and equity to its Boston rival Brand Networks.

Brand Networks said it made the acquisition to gain Shift’s customers and technology, which it has integrated into a new software platform called RelevanceRank.

According to James Borrow, former chief executive of Shift and now chief product officer at Brand Networks, the new software will help marketers turn social media posts into targeted paid advertising campaigns.

The purchase of Shift is also part of a larger strategy to grow Brand Networks’ market share. From Shift, Brand Networks will get about 250 customers as well as 86 employees, some of whom will continue to work in Santa Monica.

Shift has taken in about $14 million in venture capital investments since being founded in 2010.

Technology reporter Garrett Reim can be reached at [email protected]. Follow him on Twitter @garrettreim for the latest in L.A. tech news.