# Identity Resolution > Technology profile in The State of Streaming directory. - Profile type: Technology - Profile status: baseline - Last updated: 2026-05-03T00:00:00.000Z - Canonical URL: https://thestateofstreaming.com/tech/identity-resolution/ - Also known as: identity, identity stack, identity layer, post-cookie identity, identity solutions, cross-device identity ## Summary Identity resolution is the cross-device, cross-platform stitching layer that lets advertisers and platforms recognize the same user across browsers, mobile, CTV, and email. It is the foundational layer for addressable targeting, attribution, and cross-screen measurement after the collapse of third-party cookies as the universal web identifier. ## Definition Identity resolution is the set of techniques and vendor systems used to tie fragmented signals — a hashed email, a mobile ad ID, a CTV device graph entry, a publisher login, a household IP — back to a single, persistent representation of a person or household across devices and platforms. It exists because the third-party cookie, which served as the de facto universal web identifier for two decades, has been deprecated in Safari and Firefox by default and left in a degraded "user choice" state in Chrome after Google retired most of its Privacy Sandbox APIs in October 2025. Modern identity resolution splits into two camps: deterministic approaches, which rely on authenticated signals such as a hashed email or login (UID2, RampID, ID5 Linked ID); and probabilistic approaches, which infer the same user across devices from IP, device, behavioral, and contextual signals. Most production ad stacks now run a hybrid — authenticated IDs where consented logged-in inventory exists, probabilistic graphs and clean-room measurement where it does not, and platform-native identifiers (Apple's AdAttribution Kit, Google's PAIR, the walled-garden first-party graphs) inside the environments that won't share user data outside their walls. ## Market size US programmatic ad spending will exceed $200 billion in 2026 — the spend pool that depends on a working identity layer (as of 2026-01-27). Source: EMARKETER — https://www.emarketer.com/content/programmatic-advertising-forecast-trends-h1-2026 ## Key trends - Privacy Sandbox is effectively dead. Google retired most Sandbox APIs on October 17, 2025 and reverted to a 'user choice' model for third-party cookies in Chrome, ending the industry's seven-year wait for a Chrome-led replacement. - Authenticated IDs (UID2, RampID, ID5) are now the default plan A on the open web — but they only work where a login or email exists, leaving a long tail of unauthenticated inventory served by probabilistic graphs and contextual. - CTV is largely cookieless by design. Identity on connected TV runs on device graphs, IP-household stitching, ACR data, and platform-native IDs — not adapted web identity — which is why Roku's December 2025 UID2 adoption was a structural moment. - First-party data plus clean rooms are eating the third-party identity vendor's lunch for measurement. IAB Tech Lab is publishing ID-less guidance because the largest buyers and sellers increasingly prefer to keep raw identifiers inside their own walls and reconcile inside a clean room. - Retail-media-native identity is the fastest-growing branch — Amazon, Walmart Connect, Kroger Precision, Albertsons Media — because purchase data anchors a graph third-party vendors structurally cannot match. ## Major players - the trade desk — https://thestateofstreaming.com/companies/the-trade-desk/ - liveramp — https://thestateofstreaming.com/companies/liveramp/ - id5 — https://thestateofstreaming.com/companies/id5/ - alphabet — https://thestateofstreaming.com/companies/alphabet/ - amazon — https://thestateofstreaming.com/companies/amazon/ - infosum — https://thestateofstreaming.com/companies/infosum/ - epsilon — https://thestateofstreaming.com/companies/epsilon/ - acxiom — https://thestateofstreaming.com/companies/acxiom/ - lotame — https://thestateofstreaming.com/companies/lotame/ ## Key facts - Google retired most Privacy Sandbox APIs on October 17, 2025 and will not roll out a standalone third-party cookie deprecation prompt in Chrome, ending its seven-year effort to lead a single web-wide identity replacement. — Privacy Sandbox (Google): https://privacysandbox.google.com/blog/privacy-sandbox-next-steps - More than 16,000 publisher domains have implemented LiveRamp's Authenticated Traffic Solution, including more than 70% of the comScore 100 publishers. — LiveRamp: https://liveramp.com/our-platform/authenticated-traffic-solution-ats - Unified ID 2.0 source code was contributed by The Trade Desk to IAB Tech Lab's Partnership for Responsible Addressable Media (PRAM) Technical Working Group, moving UID2 from a single-vendor effort toward an industry-governed standard. — IAB Tech Lab: https://iabtechlab.com/the-impact-of-the-trade-desk-contributing-uid-2-0-for-industry-development/ - Roku adopted Unified ID 2.0 across its premium streaming inventory in December 2025, one of the first large CTV platforms to standardize on an open authenticated ID. — Roku Advertising: https://advertising.roku.com/learn/resources/roku-the-trade-desk-uid-2-key-takeaways - EMARKETER projects US programmatic ad spending will exceed $200 billion in 2026, the spend pool that depends on a functioning identity layer to be addressable and measurable. — EMARKETER: https://www.emarketer.com/content/programmatic-advertising-forecast-trends-h1-2026 ## Related - the trade desk — https://thestateofstreaming.com/companies/the-trade-desk/ - liveramp — https://thestateofstreaming.com/companies/liveramp/ - alphabet — https://thestateofstreaming.com/companies/alphabet/ - amazon — https://thestateofstreaming.com/companies/amazon/ - data clean rooms — https://thestateofstreaming.com/tech/data-clean-rooms/ ## External coverage - The Trade Desk: Unified ID Solution 2.0 (https://www.thetradedesk.com/unified-id-solution-2-0) - LiveRamp: Authenticated Traffic Solution (ATS) (https://liveramp.com/our-platform/authenticated-traffic-solution-ats) - IAB Tech Lab: Navigating the Agentic Frontier — IAB Tech Lab 2026 Roadmap (https://iabtechlab.com/navigating-the-agentic-frontier-the-iab-tech-lab-2026-roadmap/) - Google: Next steps for Privacy Sandbox and tracking protections in Chrome (https://privacysandbox.google.com/blog/privacy-sandbox-next-steps) - Adweek: Google's Privacy Sandbox Is Officially Dead (https://www.adweek.com/media/googles-privacy-sandbox-is-officially-dead/) - EMARKETER: Programmatic Advertising Forecast and Trends H1 2026 (https://www.emarketer.com/content/programmatic-advertising-forecast-trends-h1-2026) ## Profile Identity resolution is the part of the ad stack that does not get a marketing campaign of its own and yet decides whether the rest of the stack works. It is the layer that answers a single question on every impression: is the person about to see this ad the same person we saw yesterday on a different device, in a different app, on a different network? For two decades the answer was a third-party cookie. The cookie was never a great identity signal, but it was a universal one. That is no longer true. Safari and Firefox stripped third-party cookies out by default years ago. Chrome — the browser that carries roughly two-thirds of web traffic — spent seven years preparing a Privacy Sandbox replacement, then retired most of those APIs in October 2025 and reverted to a user-choice model that, in practice, leaves the cookie in a degraded, opt-out-prone state. The single web-wide identifier the industry was waiting for is not coming. What replaced it is not one thing. It is a layered stack. Authenticated IDs — Unified ID 2.0 from The Trade Desk, RampID from LiveRamp, ID5 — operate where a publisher has a logged-in user and a hashed email to anchor on. Where there is no login, probabilistic graphs and contextual signals carry the impression. Inside the walled gardens — Amazon, Google's PAIR, Apple's AdAttribution Kit — first-party identity stays first-party and is reconciled with advertiser data inside a clean room rather than passed through the open bidstream. CTV runs on its own logic entirely: device graphs, IP households, ACR, and increasingly platform-native IDs after Roku standardized on UID2 across its premium inventory in December 2025. The buyer's mental model has shifted accordingly. The question is no longer "what is the universal ID?" — that fight is over and nothing won. It is "what is the right identity layer for this inventory, in this jurisdiction, against this measurement question?" The vendors that thrive in this market are the ones that interoperate cleanly across all of those answers; the ones that bet on a single ID winning are the ones repricing their roadmaps. ## Tags - category - identity - post-cookie - UID2 - RampID - ID5 - cross-screen - deterministic - probabilistic - privacy-sandbox - clean-rooms - retail-media --- View this profile in a browser: https://thestateofstreaming.com/tech/identity-resolution/ Browse the directory: https://thestateofstreaming.com/tech/ Machine-readable index: https://thestateofstreaming.com/llms.txt