Google on Friday won approval from U.S. antitrust regulators to buy online advertising company Admeld.

"The Antitrust Division obtained extensive information from Google, Admeld and a wide range of market participants in connection with its merger investigation of the proposed transaction. After a thorough review of the evidence, the division concluded that the transaction is not likely to substantially lessen competition in the sale of display advertising" the Department of Justice?s Antitrust Division said in a statement.

The division?s investigation focused on the potential effect of the proposed transaction on competition in the display advertising industry. Both Google and Admeld provide services and technology to web publishers that facilitate the sale of those publishers? display advertising space. Google is a diversified software company whose offerings for publishers include an advertising exchange, an advertising network and an ad server. Admeld operates a supply-side platform (SSP) that helps publishers optimize the yield from their display advertising inventory.

The investigation determined that web publishers often rely on multiple display advertising platforms and can move business among them in response to changes in price or the quality of ad placements. This use of multiple display advertising platforms, commonly called "multi-homing," lessens the risk that the market will tip to a single dominant platform. In addition, there have been recent SSP and advertising exchange entrants in the display advertising industry. These were significant considerations in the division?s decision to close the investigation.

Google operates the largest Internet search engine in the world and one of the largest display advertising platforms. Aside from advertising-related products, Google?s software offerings include a smartphone operating system, web-based email and mapping programs. In 2010, Google had revenues of approximately $29 billion.

Google did not disclose the financial terms of the deal, although reports indicated that the company paid roughly $400 million.