The ad tech firm Conversant Inc. has agreed to be acquired for $2.3 billion in cash and stock. The Westlake Village company formerly known as ValueClick is to be bought by Alliance Data Systems Corp., a data marketing service provider in Plano, Texas.

“Gaining access to the huge data-driven platforms at Alliance Data will allow the combined entity to offer clients an end-to-end solution across all channels,” said John Giuliani, Conversant’s chief executive, in a statement.

Alliance Data offers data-driven marketing services for managing customer loyalty programs for retailers. Conversant specializes in display and video ads. Through this buy, the Westlake Village company will become a subsidiary of Alliance Data.

The deal is expected to close before the end of the year.

Conversant shares jumped 31 percent in after-hours trading Thursday to $35.05 a share on the Nasdaq stock market. Shares of Alliance Data were up $6.13, or 2.4 percent, to $259 a share in after-hours trading Thursday on the New York Stock Exchange.

Staff reporter Melissah Yang can be reached at [email protected]. Follow her on Twitter @MelissahYang for the latest in L.A. tech news.