The search giant says it can measures changes in brand awareness or active user interest by comparing two anonymised and aggregated sets of data: one, a group of thousands of web users who have seen a particular ad; and the other, a similar sized group who haven’t.

Google says the tool then measures whether there is any significant difference in searches and visits to the advertiser’s website between the two groups.

“Doing this, Google Campaign Insights can determine the incremental change that is directly attributable to the display ad campaign,” said Austin Rachlin, a blogger with Google’s Inside AdWords. “With this insight, advertisers can establish how well their display ad campaign is working.”

Previously Google’s display ad measurement capabilities had been limited to counting clicks, measuring click-through conversions and view-through conversion reporting, which measures visits to a company’s website from users who have seen that firm’s display ad in the past.

For now, the Campaign Insights tool is restricted to Google’s larger display ad clients in the US and UK, though it says it hopes to roll it out more widely over time.