Understanding the Difference Between Third-Party Cookies & Hashed Emails (and Why Hashed Emails Are the Future)

Understanding the Difference Between Third-Party Cookies & Hashed Emails (and Why Hashed Emails Are the Future)

Questions are swirling about the future of retargeting and personalized advertising, especially after Google announced that its demand-side platform, Google Marketing Platform, will no longer support third-party cookies. As someone who relies on third-party cookies to increase HCP engagement, this deprecation seems problematic. And on the surface, it is. Whenever tried-and-true ad tech goes away, especially when it enables effective audience targeting, there’ll be uncertainty. However, if you dig deeper, you’ll see that you already have alternative identity solutions that will equal—if not surpass—the efficacy of third-party cookies. How is that possible? These alternatives are built on a foundation of hashed emails.

What’s the Difference Between Third-Party Cookies and Hashed Emails?

Third-party cookies and hashed emails fundamentally do the same thing: They allow you to track HCPs’ online behavior and use that information to deliver more personalized ads to them. The difference between third-party cookies and hashed emails is how they’re built, and most importantly, how they approach online users’ privacy.

  • Third-Party Cookies: Cookie-based technology automatically uses tiny snippets of codes placed on someone’s Internet browsers to track their online behavior. Google, for example, has historically placed third-party cookies on websites to help advertisers who are using its demand-side platform (DSP), Google Marketing Platform (formerly DoubleClick), to effectively and efficiently retarget Chrome users. Third-party cookies are why you may see an ad on Adweek from Hubspot promoting its Marketing Hub after reading a piece of content on its website. The challenge with third-party cookies is that they identify people, including HCPs, on a 1:1 level, which is one reason Google is deprecating the technology (and why Apple did in 2020).
  • Hashed Email: While third-party cookies allow you to identify HCPs on the user level, hashed emails are anonymous. From a high level, alternative identity solutions that use hashed emails take someone’s email addresses and scramble them into a unique 32-character code. The catch is that HCPs have to willingly enter their email into an SSO or a publisher’s website. If an HCP consents, you can retarget them in a similar fashion that you always have with third-party cookies, albeit on an anonymous level.

Are Hashed Emails as Reliable as Third-Party Cookies?

You must stay informed about the deprecation of third-party cookies, but don’t lose sleep over it. According to a Q4 2020 study, most advertising professionals believe that email addresses will replace third-party cookies—and for a good reason.1 Here’s why:

  • The Vast Majority of People Have an Email Address: While the alternative identity solutions will require buy-in from the online community, the fact that more than 4 billion people have an email address is fantastic news as it opens the door for scale that’s equal to that of third-party cookies.2
  • Email is the Ultimate Identifier: There isn’t a more reliable way to identify online audiences than with a personal email address. Think about it: When someone logs in to a website like Buzzfeed or The Washington Post, you know it’s them because that email is unique. Said another way, Dr. Jones uses a different email address to log into Buzzfeed than his children or significant other. While hashed emails are anonymous, they still provide an undeniable link between you and your target HCP. Additionally, third-party cookies don’t work seamlessly across browsers and devices—you need complex identity graphs to make that happen—which is problematic given that the average person, including HCPs, has access to more than ten connected devices.3
  • Hashed Emails Navigate Privacy Concerns: While Google’s deprecation of third-party cookies may be more about gaining a larger share of online advertising revenue, the consensus from the online community is that third-party cookies are going away due to increasing privacy concerns. A study released in 2020 found that 74% of US respondents were more alarmed than ever about their digital privacy.4 Hashed emails require HCPs to provide their email address and consent to advertising willingly. By doing this, the digital advertising world is putting users in the driver’s seat, which will pay dividends for years to come. 

Preparing for the Future of HCP Identification

The downfall of user-level tracking with third-party cookies has been inevitable for quite some time. Despite third-party cookies enabling the status quo of the Internet (people can access free content, but in exchange, they have to see relevant advertising), the sentiment around them is overwhelmingly negative. Luckily, alternative identity solutions are already on the table, and more are coming. As these alternatives take hold, they’ll prove to be equally, if not more, impactful than their predecessor for three reasons:

  • There’s a tremendous opportunity for scale.
  • They use a fool-proof identifier.
  • They put users in the driver’s seat.


  1. Statista Research Department. Type of data that would replace third-party cookies according to marketers and publishers from the United States as of 4th quarter 2020. Statista. Published February 2021. Accessed June 1, 2021.
  2. THE RADICATI GROUP, INC. Email Statistics Report, 2021-2025. THE RADICATI GROUP, INC. Published 2021. Accessed June 1, 2021.
  3. Lionel Sujay Vailshery. Average number of devices residents have access to in households worldwide in 2020, by country. Statista. Published March 2020. Accessed June 1, 2021.
  4. The Harris Poll. 2019 CYBER SAFETY INSIGHTS REPORT GLOBAL RESULTS. The Harris Poll. Published March 30, 2021. Accessed June 1, 2021.

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