Cross-device measurement for CTV campaigns attempts to connect an ad exposure on the TV screen with a subsequent action taken on a different device — a mobile app download, website visit, or purchase on a smartphone. This matters because CTV is non-clickable: viewers cannot act on a CTV ad directly. If the ad is working — building intent, driving recall — those downstream actions happen on other devices.
How cross-device measurement works
The methodology requires a common identity linking the CTV device to the converting device. Three approaches: (1) Deterministic linking: If the viewer uses the same Google or Amazon account on both the CTV device and the converting device, the platform can deterministically link CTV exposure to the conversion within its ecosystem. Highly accurate but limited to within-platform journeys. (2) Probabilistic household IP matching: If the CTV device and the converting device share the same household IP address, cross-device graphs infer they belong to the same household. Less precise — IP addresses change, apartment blocks share IPs — but scalable. (3) Panel-based estimation: Recruited panel households have all devices measured simultaneously, allowing direct observation of cross-device behaviour projected to the broader population.
India-specific challenges
India CTV cross-device measurement faces structural friction. The fragmented identity landscape means a viewer watching JioCinema (Jio account) who then visits a website in Chrome (Google account) has no deterministic identity link between those sessions unless both platforms share a common identifier. India also has dynamic IP address assignment from ISPs, meaning IP-based household linking has higher error rates than in markets with static residential IPs. What works in India: Google ecosystem cross-device (YouTube CTV exposure to Google Chrome conversion within Google Ads), Amazon ecosystem (Fire TV/Prime Video CTV to Amazon purchase), and basic IP household matching for non-Google/Amazon journeys with 25-40% estimated error rate. What does not reliably work: cross-publisher, cross-ecosystem deterministic linking without clean room agreements.
Practical implications for India CTV planners
For campaigns where Google or Amazon handles both the CTV buy and conversion measurement, cross-device attribution is available and reasonably reliable within those walled gardens. Report these as within-ecosystem estimates, not total campaign attribution. For conversions outside these walled gardens — non-Amazon app installs, in-store purchases, phone enquiries — use incrementality test design that does not rely on individual-level identity linking. The honest framing for most India CTV advertisers in 2026: cross-device measurement is an aspiration, not a standard deliverable. Build measurement around what you can actually measure, and treat cross-device attribution estimates as directional signals rather than audited results.