NEW YORK: Expedia, the online travel company, is among the brands seeking to exploit the possibilities of cross-platform marketing by identifying the various devices used by an individual consumer.

While cookies allow the monitoring of online desktop activity, many mobile devices do not employ these tools, making it more difficult to ensure users are served relevant ads.

But by harvesting cross-screen identities, the ad industry would be able to serve ads to mobile phones based on the interests people show while surfing the web on their PCs.

"Every retailer is trying to figure out cross-platform activities," Jeff Warren, vice president of mobile and online partner marketing at Expedia, told the Wall Street Journal.

He noted that the majority of Expedia's mobile bookings were made in the days before a weekend and it was important for the company to be able to target its deals accordingly.

"Knowing when you are on your mobile phone is really key," said Warren.

Expedia has worked with Drawbridge, a mobile ad technology provider, to trial a 'triangulation' technique that tracks the ads being requested by different devices to establish if a mobile user is likely to be the same person as a desktop user.

Using this method it then sent travel offers to those people looking at travel guides in the evening in selected cities on mobile devices associated with the desktop users. If a person subsequently clicked on the ad, they would be prompted to download or use the Expedia app to book the offer.

"We have seen a direct positive relationship between spending on app downloads and someone consummating a transaction," said Warren.

"Technologies like Drawbridge give me a bit of a prayer but it is still early days."

Tapad, a company that delivers ads across devices, also looks at app downloads and purchases made within apps, as well as mobile websites visited, to help build a picture of the mobile behaviour of consumers. It then pools people showing the same purchasing intent to sell on to advertisers.

"What we are seeing now is you can really start doing advanced targeting on mobile devices," said Are Traasdahl, Tapad's CEO.

Data sourced from The Wall Street Journal; additional content by Warc staff