In an increasingly fragmented media landscape—where campaigns span linear TV, streaming, digital, mobile, and social platforms—the need for coherent and reliable measurement is becoming more urgent.

With this challenge in mind, the World Federation of Advertisers (WFA) and national advertiser associations across several countries are driving HALO, an initiative aimed at building an open, neutral, and privacy-by-design framework for cross-media measurement.

This is not a new “measurement tool” but rather an architecture that each market can implement to achieve consistent and comparable measurement.

In the following sections, we will shed light on the key questions: what HALO is, which problem it aims to solve, the current state of the project, its challenges, and what we can expect in the coming years.

What exactly is HALO?

HALO (Halo Cross-Media Measurement Framework) is a technical and governance framework—published openly—that defines how different stakeholders (advertisers, platforms, broadcasters, and measurement providers) can collaborate to produce consistent reach and frequency metrics across multiple media channels without compromising privacy.

It is built on three core pillars:

• 1. Virtual People Framework (VPF)
  Instead of identifying real users, the VPF builds anonymous virtual populations based on aggregated data and panels. These “virtual people” make it possible to estimate cross-environment exposure without tracking individuals or relying on persistent identifiers.
• 2. Privacy-Preserving Reach & Frequency Estimator (PRFE)
  A module that calculates reach and frequency by combining inputs from different platforms using secure computation techniques. The goal is to ensure that no party can access another’s raw data.
• 3. APIs y arquitectura abierta
  HALO defines public specifications that allow any market to implement its own system, with comparable metrics for all and without proprietary dependencies.

What problem is HALO trying to solve?

The challenges HALO aims to address are not new:

• 1. The growing fragmentation of media
  Advertisers invest simultaneously in linear TV, CTV, YouTube, social platforms, and streaming services. Each environment uses different methodologies, resulting in silos that are difficult to reconcile.
• 2. The disappearance of identifiers and cookies
  Many earlier attempts at unified measurement relied on persistent IDs. That path is no longer viable. HALO embraces privacy-by-design models where re-identification is not possible.
• 3. Excessive frequency and inefficient spend
  The lack of a unified view leads to duplicated exposures, saturation among certain groups, and overall inefficiency. With a consolidated perspective, investment and planning could be significantly optimized.
• 4. The need for a neutral framework
  The industry is wary of solutions controlled by a single party. HALO is driven by advertisers and built with an open structure, aiming to create common ground that all stakeholders can accept.

What is the current status of the project?

HALO is an architecture already published publicly, with technical documentation and open repositories. However, its real implementation depends on each individual country.

As of today:

• - The technical community remains active
  

  There are recurring town halls where the roadmap is updated, documentation is published, and progress is discussed.

• - Implementations are already underway

  As of now, the most advanced markets are the United States and the UK.

  In the United States, the project known as “Aquila” has contracted providers such as Kantar and Accenture to build panels and technical modules, and is developing pilot tests throughout 2025. All indications suggest it will take off in 2026.

  In the UK, the “Origin” project has progressed through multiple beta tests with more than 30–35 advertisers and is currently developing a national panel and governance contracts.

• - HALO is not a final product, but a technical “roadmap”
  This means there will be no single global launch; instead, there will be local implementations, each under its own governance structure.

Challenges Ahead

HALO has set a promising path, but implementing it at scale is far from trivial.

These are the main obstacles:

• 1. Privacy and re-identification risks

  Virtualized models reduce risks, but regulators and privacy advocates are closely scrutinizing how datasets are combined. Any vulnerability could slow adoption.

• 2. Real governance and neutrality

  Deciding who audits, maintains the models, validates the data, or participates in committees is not straightforward. Market trust depends on it.

• 3. Costs and panel scalability

  Working with robust panels and reliable calibrations requires significant investment. In some markets, this can be a barrier.

• 4. Alignment of platforms and broadcasters

  Participation from major players (Google, Meta, Amazon, national broadcasters, AVOD/FAST platforms…) is crucial. Without their data, the cross-media view remains incomplete.

• 5. Different paces across markets

  Not all countries share the same regulatory framework, technological maturity, or consensus among stakeholders.

Conclusion

HALO is increasingly emerging as one of the most strategic projects for cross-media measurement in the advertising industry. It is not just a concept: its technical components (VPF, PRFE, APIs) are mature, its model is open and modular, and local implementations are already underway in key markets such as the UK and the US.

However, turning a framework into a global standard involves significant challenges: coordination, resources, governance, and adoption. The ultimate success will depend on the collective willingness of advertisers, agencies, media, and national associations to commit to a shared vision. If that collaboration flourishes, HALO could transform the way we measure and optimize advertising campaigns worldwide—with greater transparency, efficiency, and respect for privacy.