Online research firm comScore announced that it's buying Seattle's AdXpose for $22 million.

The deal comes four months after AdXpose restructured, took $3 million in venture funding and changed its name, from Mpire.

AdXpose is an advertising analytics company that handles 30 to 50 billion ad optimizations per month. Since 2008 it's been led by Kirby Winfield, a veteran of Marchex and Go2Net.

It started in 2004 as a comparison shopping site led by Matt Hulett, now head of RealNetworks game business. The site changed its business plan several times, becoming an ad network called WidgetBucks in 2007 and an analytics company in 2009.

Founder and Chief Technology Officer Greg Harrison said there were "a couple pivots here and there" but the company continued to build upon its technology.

"The migration from the WidgeBucks world where we were instrumenting and monetizing advertising data led to the core technologies that are now the underpinnings of AdXpose and that is what has taken off ... and garnered attention from groups like comScore," he said.

AdXpose has 22 employees, including 19 full-timers. Harrison said it's going to keep expanding.

"The bottom line is we'll be growing a nice team here in the Northwest and expanding on the product line for AdXpose," he said.

ComScore will incorporate AdXpose's ad verification and optimization tools into its "ad effectiveness product suite," the company said in its release.

"Through the integration of these capabilities, comScore will be able to further its mission to develop the most comprehensive end-to-end suite of digital advertising analytics," Magid Abraham, comScore president and chief executive, said in the release. "With audience-buying becoming increasingly prevalent in digital media planning today, there is a growing demand for analytical tools that enable greater transparency and accountability in ad delivery."

The deal is expected to close in about two weeks.

ComScore's been shopping in Seattle before. In 2008 it bought mobile analytics company M:Metrics, and eventually it will consolidate AdXpose's downtown office with the M:Metrics group in Pioneer Square.