Yahoo has announced the purchase US-based online ad exchange Right Media, in a deal worth $680m (£340m).

The acquisition is a step towards competing with Google, which recently acquired online ad network DoubleClick.

Back in October, Yahoo bought 20% of Right Media for $45 million and today’s announcement will see it buying the remainder of the company.

Right Media is one of the largest online ad exchanges, which serve up banner ads and other ad formats to less-trafficked websites than traditional ad networks.

According to Terry Semel, chairman and CEO of Yahoo:

“The acquisition of Right Media will further Yahoo’s goal to create the industry’s most open, accessible and vibrant advertising marketplace, which will help democratise the buying and selling of digitally enabled advertising.”

Launched in April 2005, Right Media is one of the largest online ad exchanges, which serve up banner ads and other ad formats to less-trafficked websites than traditional ad networks.

Right Media has attracted around 20,000 advertisers, publishers and networks to its online advertising exchange. Yahoo said it planned to increase its participation in the exchange as both a buyer and seller to increase the liquidity of Right media as an advertising media marketplace.

Susan Decker, CFO of Yahoo said the platform would offer more choice for advertisers and publishers:

“Yahoo! is the largest online publisher and one of the leading ad networks on the web, and we believe it is in our strong financial interest to make sure there is a widely adopted, neutral, frictionless exchange that enables publishers and advertisers to benefit from a basket of the best solutions rather than having to accept a single solution from one of the larger players.”