Yahoo has acquired video advertising platform Brightroll for $640m, marking its second major acquisition under CEO Marissa Mayer after the $1.1bn Tumblr deal last year.

The latest deal will sharpen Yahoo’s focus on video ads, which will help offset its sluggish growth and bolster declining display ad revenues.

Yahoo CEO Marissa Mayer said: "Acquiring BrightRoll will dramatically strengthen Yahoo’s video advertising platform, making it the largest in the US. BrightRoll is the industry’s leading programmatic video advertising platform for reaching audiences across web, mobile andconnected TV.

"BrightRoll is a large, growing and profitable business with net revenues expected to exceed $100 million this year.

"I’ve spent time with Tod Sacerdoti and his leadership team and I cannot wait to have him, his vision, and his team here at Yahoo."

In addition to enabling advertisers to plan and focus video ad campaigns, Brightroll’s platform allows publishers to include advertising lists into their content.

Brightroll’s video platform can be accessed across web, mobile and connected devices such as TVs.

The eight-year-old San Francisco-based firm currently serves over 80 of America’s largest advertisers.

Mayer added: "BrightRoll provides an effective solution, aggregating high-quality publishers together into a unified network and utilising programmatic advertising to allow real-time buying on the largest set of online video advertising inventory available.

"BrightRoll’s approach not only benefits advertisers and publishers, but also improves experiences for consumers, through better quality, more relevant advertisements."