What is cross-device targeting?
Cross-device targeting is the ability to recognize that several devices, such as a phone, laptop, tablet and smart TV, belong to the same person or household, and to target and measure ads across all of them. It lets advertisers carry a message across screens, cap frequency per person and credit conversions that happen on a different device.
How cross-device targeting works
Platforms build a device graph, a map that links devices to a person or household. There are two main methods:
Deterministic matching: links devices through a known identifier, usually a login. If someone signs in to the same account on their phone and laptop, the platform knows both devices are theirs. This is accurate but limited to logged-in users.
Probabilistic matching: infers links from signals like shared IP address, location patterns, device type and timing. It covers more devices but is less precise, and its use is restricted by privacy laws and platform policies.
Households add another layer. Devices on the same home network, including connected TVs, can be grouped so that a TV ad and a later mobile ad count toward the same household.
The quality of a device graph depends on how many logged-in users the platform has and how fresh its links are, so match rates differ from one platform to another.
Once devices are linked, the DSP can apply one audience segment, one frequency cap and one attribution model across the whole graph.
Why cross-device targeting matters
People rarely complete a purchase on the device where they first saw an ad. Without cross-device linking, each device looks like a separate user, which causes three problems:
Wasted frequency: the same person sees an ad five times on mobile and five more on desktop because the platform thinks they are two people.
Broken sequencing: a story that starts on CTV cannot continue on mobile.
Undercounted results: a laptop conversion after a mobile ad view goes uncredited, so attribution undervalues the campaign.
Cross-device targeting fixes these by treating linked devices as one audience member, which means more accurate reach counts and less spend lost to overexposure.
Privacy rules shape what is possible. Links based on consented logins are the most durable, while fingerprinting-style methods are restricted on major mobile platforms and under many privacy laws.
Cross-device targeting vs retargeting
Retargeting shows ads to people who already interacted with your brand, such as site visitors. Cross-device targeting is a capability rather than a tactic: it decides which devices belong to the same user. The two often work together, for example retargeting someone on their phone after they browsed your site on a laptop.
Cross-device targeting with AdGeeks
Large platforms have strong signed-in data: Google behind DV360, and Amazon across shopping and streaming behind Amazon DSP. AdGeeks traders use each platform's cross-device capabilities to set frequency caps across screens, sequence creative from TV to mobile and report conversions that happen on a different device from the ad view.
