The deal, which has been in the works for almost a year, may affect billions of ads a day, changing the way agencies and big companies run and monitor campaigns. This is part of a broader push by Google to attract more big brands, which have traditionally spent most of their money on TV.
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"To really crack the nut and bring brand dollars to digital advertising, you have to crack the brand-measurement nut," says Neal Mohan, vice president of display advertising at Google. "This integration and partnership with comScore is our bet on real-time audience measurement."
Google already dominates performance-related ads online through its leading search engine, limiting future growth there. Brand advertising is a big market that the company has yet to embrace fully, giving it more room to grow.
The total brand advertising market, which includes digital, TV and more traditional offline ads, is worth at least $300 billion a year. As more of this moves online, Google is positioning itself and partnering with more companies to grab as much of this money as possible.
(Read more: Fox (and Mindy) push limits of native advertising)
Digital brand advertising spending will grow from $18 billion in 2013 to $31 billion by 2017, while spending on direct response, or performance, ads online will climb from $25 billion to $32 billion, according to eMarketer.
Google has been working on its own ad-measurement technology for years. But as the company focuses more on brands, it has become more open to working with third-party measurement firms such as Nielsen and comScore. That's because big ad spenders require independent data on how their campaigns are going and want the data to be comparable with the information they get on the performance of their TV ads.
"The end game is to integrate this with TV measurement," comScore President Serge Matta says. "Most of the ad dollars are on TV, and over time that will shift to digital, and you will want to measure this in real time across all platforms."
Google seems to be favoring comScore over Nielsen as it adopts more third-party measurement services.
(Read more: Google bought $750 million Lenovo stake on January 30)
"DoubleClick is an open platform, and we work with other measurement partners like Nielsen. But this is a deeper integration with comScore," Mohan says. "We've been really impressed with feedback on vCE from the market, including some large advertisers like Kellogg."