Unified ID (UID2) Alternatives in 2025: What to Use, When, and How to Migrate
·September 10, 2025
·8 min read
If you rely on Unified ID 2.0 (UID2) for open-internet addressability, you’re probably asking the same question many ad tech teams are asking in 2025: What else should we run in parallel to stay compliant, keep scale (especially on Safari/Firefox and CTV), and preserve measurement fidelity?
Short answer: there’s no single replacement. Most high-performing stacks mix 2–4 IDs plus Chrome’s Privacy Sandbox capabilities. Below is a practitioner’s guide to the strongest UID2 alternatives and complements, how they differ, and how to migrate with minimal disruption.
As of September 2025, all facts and links are up to date. Re‑validate vendor docs and legal guidance for your regions before shipping changes.
TL;DR — Quick Picks by Scenario
- EU-first publishers worried about GDPR and centralized control: Prioritize ID5 + Prebid SharedID; consider adding LiveRamp RampID for deterministic collaborations.
- Safari/Firefox reach on unauthenticated web: Start with Prebid SharedID and ID5; add Lotame Panorama ID for incremental recognition.
- CTV-heavy advertisers with good login/CRM coverage: Keep UID2; layer LiveRamp RampID or Neustar Fabrick for cross-platform dedup and clean-room measurement.
- Enterprise people-based measurement and partnerships: LiveRamp RampID or Merkle Merkury; plan for clean room workflows and mapping files.
- Chrome strategy: Continue cookies where viable; experiment with Topics/Attribution Reporting from Privacy Sandbox as a parallel capability.
Why Look Beyond UID2 (Even If You Keep It)
UID2’s strengths are real: a consented, deterministic framework with strong CTV traction and broad SSP/DSP support. The governance includes opt-out enforcement at token generation (the optout_check parameter) and token rotation/revocation in SDKs, which is useful for compliance programs, per the official UID2 documentation in 2025 from Unified ID’s portal (token generation and opt-out).
The gaps that typically push teams to broaden their mix:
- Coverage is gated by authenticated traffic; many publishers still have limited login adoption.
- Regional compliance posture varies by implementation; legal reviews are non-negotiable in the EU.
- Addressability on Safari/Firefox for non-logged-in users remains hard without augmenting IDs.
- Some stakeholders prefer less centralization or more publisher-first options.
How We Evaluated Alternatives (Weighting)
- Compliance & governance: 25%
- Scale & match rate (web/CTV, Safari/Firefox): 25%
- Interoperability (Prebid/SSP/DSP/clean rooms): 20%
- Measurement fidelity: 15%
- Migration effort & cost: 10%
- Vendor stability & transparency: 5%
Every option below includes: where it shines, when not to choose, and migration notes from a UID2-centric stack.
1) ID5 ID — Publisher-Centric Coverage Beyond Third-Party Cookies
What it is and why it’s different
- ID5 provides a shared, privacy-by-design identity that’s issued and used in first-party contexts. It’s designed to operate without third-party cookies and plugs into header bidding via Prebid’s user ID ecosystem. See ID5’s publisher documentation for consent flow and Prebid integration specifics in 2025 (ID5 for Publishers).
Where it shines
- Safari/Firefox support and unauthenticated web contexts where you still have first-party storage and valid consent.
- Straightforward Prebid enablement and broad demand-side recognition through EIDs.
Watch-outs
- Performance varies by your publisher footprint and which demand partners can decrypt and transact on the ID5 signal.
Migration notes from UID2
- Low to moderate lift if you’re already on Prebid: enable ID5 in your userId configuration, pass eids, and monitor win rate/CPM deltas by browser. ID5’s guidance aligns with TCF/US Privacy signaling, which simplifies consent handling (ID5 for Publishers, 2025).
2) LiveRamp RampID — Deterministic People-Based Identity for Enterprise Workflows
What it is and why it’s different
- RampID is a pseudonymous, deterministic identifier backed by LiveRamp’s identity resolution and authenticated traffic solutions (ATS). It’s widely interoperable with SSPs/DSPs/CDPs and clean rooms. LiveRamp’s own docs outline RampID types, creation, and privacy controls; see the 2025 identity and RampID interpretation pages (LiveRamp RampID identity resolution).
Where it shines
- Cross-device deduplication and measurement via mapping files and clean-room collaborations, especially for advertisers with strong CRM data.
Watch-outs
- Requires contracting, data onboarding, and governance reviews. Best suited to teams ready for enterprise-grade workflows.
Migration notes from UID2
- Treat RampID as a complementary deterministic key across destinations. Work with your account team to enable RampID where it can be the default identifier and align clean-room schemas and dedup logic (RampID default identifier notice, 2022—still referenced in 2025 docs).
3) Prebid SharedID — The Low-Lift, First-Party Baseline
What it is and why it’s different
- SharedID is a publisher-centric, first-party identifier in the Prebid ecosystem. It respects TCF/US Privacy signals and is easy to enable in Prebid.js. The module and consent handling are documented by Prebid.org (User ID module configuration).
Where it shines
- Minimal engineering lift, strong fit for Safari/Firefox testing, and clean alignment with Prebid’s privacy posture.
Watch-outs
- Effectiveness depends on partner support and your own footprint; it’s not a standalone replacement for deterministic, consented people-based IDs.
Migration notes from UID2
- Very low lift: enable SharedID alongside UID2 and measure incremental lift. Prebid’s PB9 notes also explain the shift toward eids arrays for interoperability (Prebid PB9 notes, 2025).
4) Google Privacy Sandbox — Chrome Capabilities, Not a Drop-In ID
What it is and why it’s different
- Privacy Sandbox provides on-device privacy-preserving APIs (Topics, Protected Audiences, Attribution Reporting, Fenced Frames) rather than user-level IDs. Google’s official status and updates outline current capabilities and timelines in 2025 (Privacy Sandbox developer status).
Where it shines
- Chrome remarketing and measurement experiments where you need to respect evolving privacy constraints while keeping some audience/attribution signal.
Watch-outs
- After Google’s cookie deprecation U-turn, industry momentum is mixed. AdExchanger reporting in 2025 captured flat Topics API adoption signals and shifting focus to Incognito/IP Protection—useful context for planning (AdExchanger 2025 analysis of Sandbox adoption).
Migration notes from UID2
- Don’t expect parity with deterministic IDs. Treat Sandbox as a parallel Chrome channel capability while maintaining cookie-based methods where viable and running other IDs for the open internet.
5) Lotame Panorama ID — Graph-Backed Coverage Across Browsers and CTV
What it is and why it’s different
- Panorama ID is Lotame’s people/device-level identity within its graph, designed to work in cookieless contexts and interoperable with major environments. Lotame provides technical docs on its tagging and syncing and has emphasized interoperability, including adoption of UID2 in 2024 to improve portability (Lotame’s UID2 interoperability announcement, 2024).
Where it shines
- Complementing first-party IDs on Safari/Firefox and extending recognition across devices/CTV via Lotame’s identity services.
Watch-outs
- Some performance claims are vendor-reported; validate with your SSP/DSP logs. Deeper features may require contracts beyond simple tag activation.
Migration notes from UID2
- Moderate lift: add Lotame’s tag/sync, enable Panorama ID, and evaluate incremental win rate and conversion lift alongside UID2 and first-party IDs. Lotame’s developer references outline implementation details for Sync.js and Lightning Tag (Lotame Sync.js guide).
6) Neustar (TransUnion) Fabrick ID — Interoperable ID Used by Large Agencies
What it is and why it’s different
- Fabrick is positioned as an open, interoperable alternative used in multi-ID strategies by major buyers. For example, OMD publicly discussed using Fabrick alongside UID2 and RampID in cross-platform activation, per AdExchanger’s 2024–2025 conference coverage (OMD’s alternative ID strategy at Programmatic I/O).
Where it shines
- Portfolio strategies where advertisers want deterministic identity without being tied to a single vendor, plus broad programmatic activation.
Watch-outs
- As with other enterprise IDs, expect contracts, data onboarding, and governance work. Confirm current web/CTV partner coverage directly with TransUnion/Neustar.
Migration notes from UID2
- Run Fabrick alongside your current IDs, then calibrate deduplication and frequency management across partners to avoid over-delivery.
7) Merkle Merkury — First-Party Graph and Clean-Room-Centric Activation
What it is and why it’s different
- Merkury is Merkle/Dentsu’s identity and data platform focused on first-party graphs, privacy program rigor, and collaboration/activation via partner ecosystems and clean rooms. The product site outlines the platform’s approach and use cases (review 2025 content on the official site) (Merkury product overview).
Where it shines
- Brands with robust CRM data, looking to unify customer views and activate across the open internet with strong governance and measurement.
Watch-outs
- Requires enterprise data readiness, integration with your CDP/clean room stack, and multi-team collaboration (marketing + data + legal).
Migration notes from UID2
- Treat Merkury as a strategic layer for people-based identity and measurement; keep UID2 for supply that recognizes it, while ramping Merkury-based activation and dedup in clean rooms.
Not Included This Round: SWAN (Secure Web Addressability Network)
SWAN has been framed as a decentralized, consent-centric framework. However, we didn’t locate current, citable technical documentation this cycle to describe production-ready Prebid/header bidding integrations with confidence. If you’re exploring SWAN, review the latest specs, partner lists, and legal guidance on the official site and test in a contained environment before committing.
When to Keep UID2 vs. When to Switch or Complement
Keep UID2 (often as part of a mix) if
- You have strong authenticated audiences (logins, CTV apps) and stable performance with your current SSP/DSP stack.
- Your legal review affirms your consent UX and disclosures for the regions you operate in.
Complement or pivot if
- You need more reach on unauthenticated web and cookie-restricted browsers (Safari/Firefox).
- You want a stronger EU posture and/or wish to diversify away from a centrally governed framework.
- Your measurement requires robust cross-device deduplication and clean-room collaboration at enterprise scale.
Practical Migration Playbook (From UID2 or Cookie-Centric Setups)
- Harden your Prebid stack
- Enable SharedID and ID5 in the userId module and pass eids consistently; ensure TCF/US Privacy strings flow end to end. Prebid’s official module docs remain the canonical reference in 2025 (Prebid user ID module).
- Run a parallel-key strategy
- Operate multiple IDs simultaneously (e.g., UID2 + ID5 + SharedID + Panorama) and measure incremental lift by browser/channel. Use bidder-level analytics to track win rate, CPM, and CPA movement.
- Prepare for enterprise graphs
- If adopting RampID, Fabrick, or Merkury, inventory your destinations, contracts, and legal bases. Align clean-room schemas and set up mapping files for cross-device deduplication as described in LiveRamp’s documentation (RampID mapping files, 2025).
- Chrome-specific planning
- Maintain cookie-based approaches in Chrome where allowed; treat Privacy Sandbox APIs as experiments with specific use cases (retargeting via Protected Audiences, attribution via Attribution Reporting). Track adoption and policy signals via the official status page (Privacy Sandbox status).
- Compliance hygiene and revocation
- Update consent UIs to explain each identifier and data flow. Enforce revocations and retention policies. If you continue using UID2, ensure the optout_check logic is honored at token generation and refresh per the 2025 docs (UID2 opt-out enforcement).
Lightweight Comparison Snapshot
- ID5: Best for cookie-restricted browser coverage via first-party contexts; quick Prebid enablement; variable partner recognition.
- RampID: Best for enterprise people-based measurement and clean-room collaboration; higher onboarding/governance effort.
- SharedID: Best low-lift baseline in Prebid; not a standalone deterministic solution.
- Privacy Sandbox: Chrome capabilities for remarketing/attribution; not a user-level ID replacement.
- Panorama ID: Best as an augment to first-party IDs for added graph coverage across web/CTV; validate vendor claims with your data.
- Fabrick ID: Best in multi-ID buyer portfolios seeking interoperability without lock-in; enterprise onboarding expected.
- Merkury: Best for brands with strong first-party data and clean-room readiness; strategic investment.
Final Advice
- Mix, don’t bet-the-farm: Run at least two IDs plus Sandbox capabilities in Chrome. Measure incrementality, not just match rate.
- Treat compliance as a product feature: Bake consent and revocation into your engineering acceptance criteria; log everything.
- Revisit quarterly: Identity tech, browser policies, and partner coverage change quickly. Re‑review vendor docs and trade press every quarter. For example, AdExchanger’s 2025 reporting captured shifting industry sentiment on Sandbox adoption and priorities—use such context to steer tests and expectations (AdExchanger 2025 Sandbox sentiment).
If you want a second pair of eyes on your migration plan, start with a 2–3 week pilot across two IDs plus Sandbox, then scale what moves business KPIs while staying well within your compliance guardrails.
