Can Email Be The Next Big Online Identifier?

Can the email address be the next big online identifier?

With third-party cookies soon to leave the scene, the ad industry is casting about for an alternative identifier, one preferably based on first-party data, collected with consent.

Email in particular is being heralded as a way to maintain identity in the face of third-party cookie loss. And numerous industry solutions are being built with email as the foundation.

There’s the next iteration of The Trade Desk’s Unified ID, which aims to create a single sign on for browsing across the open internet, and LiveRamp’s Authenticated Traffic Solution, which allows publishers to match consented data, commonly an email address, with the LiveRamp identity graph.

The IAB’s Project Rearc, a cross-industry initiative with the grand ambition of creating a framework that will eventually help rearchitect how digital marketing functions, is working on proposals for technical standards to underpin a consumer-provided ID tied to privacy preferences. A sufficiently encrypted email address has been floated as one possible contender. (The Trade Desk recently said its updated Unified ID will build on the Rearc guidelines.)

But questions of scale, privacy compliance and viability remain. Can the email address be the next big online identifier?

AdExchanger checked in with the experts.

Katie Anderson, programmatic media lead, PMG

No question email could be a viable option to identify users online. Email has an infinitely longer look-back window, can seamlessly map together devices at the user level and incomparable accuracy. It’s why tech companies like Facebook and Amazon enjoy booming ad sales for their unique ability to personalize ads to all of the activities a user has associated with their email login and viability sans cookie.

The big benefits of email, though, are also its Achilles’ heel as a full replacement for the cookie. It’s not universal, it requires time and trust from a user and the quality gained from an actively opted-in audience means a tradeoff with scale across the open exchange. With privacy and transparency top of mind, I anticipate that the more widely-used currency for audiences and tracking will need to use a combination of email with other high-quality sources, such as contextual technologies and log-level data, to tell the full story vs. full reliance on one single source as it has historically.

Alex Magnin, founder, The Unwinder

Email is no panacea for the shrinking of the basis on which open web and app monetization rests. If you can get an email and a logged-in experience, great! If a consumer values you that much, you can monetize that relationship in many mutually beneficial ways, including targeted advertising.

My bet is a lot of publishers won’t be able to collect enough email addresses. Offerings like Sign In with Apple don’t make it easier. Ad tech solutions – whether probabilistic, contextual, finger-printy, browser-based or Chrome-delay lobbying – will help ad buyers with testing, media mix modeling and Bayesian inference.

But at the end of the day, the changes of regulators, Apple and maybe Chrome make web-based advertising less efficient on average.

Tom Kershaw, CTO, Magnite

An email address is universally considered to be PII, so as such it can never be a valid identifier for online advertising. It can, however, be used to derive an identifier either by hashing/anonymizing the value or by using it to link together a series of first-party values.

The bigger issue is whether consent to use email addresses can be achieved at sufficient scale to have utility. Email will have a role in the post-cookie world, probably a significant one.

However, it will also coexist with other solutions, such as first-party data, browser-centric systems and innovations that we are still working on as an industry. Will it entirely replace the third-party cookie model? Absolutely not. But it will be a critical element of a consented, privacy-first internet going forward.

Jakob Bak, CTO and co-founder, Adform

Email won’t fly in the long term or the short term. It might have been okay five years ago, but we live in a GDPR world today and sharing PII out there in the open ecosystem in any way – I don’t see that happening.

That said, there are some big publishers working together, slowly, at the national level in certain countries with a focus on logged-in users and hashed email. The European netID Foundation in Germany, for example, is a login consortium that has some traction, and they plan to send a login ID out into the ad tech ecosystem. We’ll see that sort of thing happen. But when I visit CNN to read the news, I won’t log in unless I’m completely forced to, and I believe many others are the same as me. And so we will continue to see the majority of traffic not associated with a login.

We estimate that around 10% of traffic today has logged-in IDs attached to it, and that number could grow to maybe 20% over the next few years. But what about the majority of traffic? Email does not fully solve the problem we need to solve.

Matt Keiser, CEO and founder, LiveIntent

The fact that email went from being primarily known as “offline” to being key to identity is an endorsement of email’s ability to act as a bridge: from advertising to marketing, from offline to online, from logged-in media owned by walled gardens to inventory monetized by publishers, and, now, from third-party cookies to an era of first-party data.

The email address is the workhorse of CRM and the fulcrum of identity, and it’s what we use to log into apps, devices, platforms and channels.

In this new era, the email address will be what empowers publishers to enjoy all the control and advantages that the walled gardens enjoy by bringing brands the addressability, features and functionalities that have made them the preferred destination for brand and agency budgets.

Responses have been edited and condensed.

Enjoying this content?

Sign up to be an AdExchanger Member today and get unlimited access to articles like this, plus proprietary data and research, conference discounts, on-demand access to event content, and more!

Join Today!


  1. Users: We want privacy and don’t want to be tracked across the web even if it’s anonymous.
    Google/Apple: Let’s help users reach that goal by blocking 3rd party cookies to limit tracking.
    Ad Tech: We’ve never been able to collect email addresses at scale with user consent, but since Google and Apple are limiting tracking, let’s start using email addresses to invade their privacy more thoroughly than we ever could with cookies!

  2. Sebastian

    This is not about user’s privacy, this is about Google walled garden and CPM value.
    If you do not want to be tracked you can easily turn off 3rd party cookies in your browser by yourself, you do not need Chrome to block anything.