Zillow, the massive online real estate site, has agreed to acquire Trulia, the less-massive but still very large real estate site, for $3.5 billion. The deal is a stock-for-stock transaction.

Trulia isn’t going away or anything – as the company will continue to operate both the Zillow and Trulia brands.

“Consumers love using Zillow and Trulia to find vital information about homes and connect with the best local real estate professionals,” says Zillow CEO Spencer Rascoff. “Both companies have been enormously successful in creating compelling consumer brands and deep industry partnerships, but it’s still early days in the world of real estate advertising on mobile and Web. This is a tremendous opportunity to combine our resources and achieve even more impressive innovation that will benefit consumers and the real estate industry.”

The company created by this acquisition will hold sway over a very large chunk of the online real estate listings market. Last month, Zillow and Trulia amassed 83 and 54 million unique users, respectively. Both Zillow and Trulia say that the deal will lead to faster innovation, better access to real estate market data, and “enhanced value and ROI for advertisers.”

“Both Zillow and Trulia are primarily media companies, generating the majority of revenue through advertising sales to real estate professionals. Despite continued growth as public companies, significant opportunities of scale remain as the majority of advertising dollars in the real estate sector have yet to migrate online or to mobile,” said the companies in a press release.

“Trulia and Zillow have a shared mission and vision of empowering consumers while helping real estate agents, brokerages and franchisors benefit from technological innovation. By working together, we will be able to create even more value for home buyers, sellers, and renters, as well as create a robust marketing platform that will help our industry partners connect with potential clients and grow their businesses even more efficiently. Our two companies share complementary employee cultures with innovative, consumer-first philosophies and a deep commitment to create the best products and services for our industry partners,” says Trulia CEO Pete Flint, who will stay on to run Trulia and report to Rascoff.

Image via Zillow, Facebook