Key Points

  • Hashed email is a data collection solution that has evolved to meet the needs of the digital advertising industry in a changing data regulatory landscape. 
  • With third-party cookies, a previously vital means for data collection within the ad tech ecosystem, on their way out the door, email hashing has emerged as an alternative method.
  • Because of their increasing popularity, email hashing poses an exciting opportunity for publishers to access critical data sets about online users
  • Playwire’s hashed email API makes the email hashing process simple and straightforward, further cementing our data foothold even with the end of third-party cookies approaching.

In the past few years, there’s been some building drama in the world of ad tech. 

The antagonist? Third-party cookies.

Since the announcement that third-party cookies would be phased out, the search for a magical solution to replace them has been on. Luckily, the timeline to end third-party cookies was pushed out shortly after the original announcement, which has allowed one unlikely hero to emerge: hashed email.

So what is email hashing? And why should you give a hoot?

Keep reading to find out.

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The Publisher's Guide to Data Management Platforms

The Publisher's Guide to Data Management Platforms

What is Email Hashing?



Email Hashing: Defined

"Email hashing" is the process of taking an email address and transforming it into an unrecognizable string of letters and numbers.

Alright, that’s all well and good, but why the heck would you care about hashing an email as a publisher?

Like any good movie, let’s begin with the backstory.

A Recent History of Cookies, Data, and Audience Targeting

We can’t talk about email hashing without first covering the landscape from which it came. 

A few years ago, several major internet browsers made the announcement that they would be making big changes to their third-party cookies policies. More specifically, they would stop using them.

Google, the big poppa of the entire digital advertising landscape, then announced in early 2021 that they would be phasing out third-party cookies as well, though the timeline for this monumental change has shifted since then.

Regardless, this was a big deal. Massive. Like, major motion picture explosion massive. 

Until that point, and still, to this day, third-party cookies were the way that almost everyone on the internet, especially those of us in ad tech, reached their target customers. We used third-party cookies to identify site visitors and gather information to improve digital marketing efforts. When you’re familiar with users’ interests, you can increase the chances of a campaign’s success by tailoring content to your target audience.

Online advertising has depended heavily on this method of identification for ad campaign strategy with audience targeting being mission-critical. And without a way to identify users, targeting is difficult, if not impossible. 

Without this user data, all publishers and advertisers have to go off of is contextual information about the website the user is on. To say this kind of guesswork is limiting would be an understatement. 

So when the browsers stopped working with third-party cookies, everyone freaked out. And with Google shortly behind, the search for a solution began.

So, Hashed Email is the Solution?

Now that we’ve entered the third act, the biggest solution to have emerged is the use of email addresses as user identifiers. 

Everyone has an email address. And people use their email addresses across multiple sites to log in or sign up for newsletters. 

Publishers who collected these emails could create unique identities for advertisers to track users from site to site. 

Sounds great, right?

There was one problem: people were uncomfortable with the idea because it didn’t protect users’ privacy. No one wanted to get spammed constantly. And if those email addresses were just in the wild for everyone to see, that would be a nightmare.

That’s where email hashing comes in.

To hash an email address means to encrypt it. During the hashing process, the original email address is put through an algorithm that turns it into a 32, 40, or 64-character code. And this code is very difficult to reverse. If you don’t have the unique key that was used to encrypt it, you can’t unencrypt it. 

That’s important for a few reasons — 

  • It protects user's personal data, which is obviously good.
  • It protects publishers from legal risk and reputational harm.

The Power of Cross-Channel Data Sharing With Hashed Email

Everyone in the ecosystem should want to ensure emails are encrypted. But this level of collaboration goes a step further.

Publishers also benefit when everyone uses the same encryption key. This is the true movie-like magic of hashed emails. 

There are a few standard encryption mechanisms that, if everyone follows the correct steps, produce an identical output of numbers and letters.

Here’s an example — 

If you take an email address, let’s say:, and put it through one of the industry standard hashing mechanisms like SHA256, that email will be immediately recognized by players up the ad tech chain, and connected with anything they know about that user, which will make them instantly more valuable to advertisers.

This allows you to maximize the value of your inventory, simply by passing this information upward. (Oftentimes, we’ve seen CPMs double on a specific user impression the second a hashed email is known).

So, hashed email allows the ad tech industry to —

  • Track users across sites
  • Trust that the hashed email belongs to the same person
  • Collect user data in a way that is private and secure
  • Share information about a single user between multiple data platforms
  • Allow advertisers to use this rich data about users to better target campaigns (thus making them willing to pay much more for an impression)

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OP.GG Case Study

Learn how OP.GG created an entirely new revenue stream by partnering with Playwire!

Concerns With Hashed Email

Is it a perfect solution? Of course not. This is ad tech we’re talking about. (And every movie needs its conflict.)

Here are some potential pitfalls or soft spots to keep an eye on.

Tracking the Same User Across Different Email Addresses

There is no way to track users across email addresses. 

So, if a user logs into one computer with a business email address and another with a personal email address, it won’t matter if both emails are connected to the same device or IP address. Publishers won’t be able to track them since the email addresses aren’t identical.

Privacy Issues

Data privacy laws are rapidly evolving all over the world. So, although hashed email has been greenlit for now, nothing is set in stone.

If recent years have taught us anything, it's that we need to be prepared for sudden changes. 

Even now, there are already plenty of restrictions on hashed email — GDPR, CCPA, and other state and national privacy laws have just as much to say about these topics as they do about cookies. 

Some publishers have to update their privacy policies, ensuring they provide explicit opt-out opportunities among other things. In the EU, consent management platforms are required to state that a site might use this information so users can make informed consent decisions.

If that sounds like a headache, it’s because it is. And the shifting requirements are only making publishers and advertisers dizzier as time goes on. 

There’s good news, though. A good CMP will handle the majority of the grunt work for publishers when paired with a good data collection strategy. But publishers will still need to make updates and provide consistently accurate information in their privacy policies.

Unlock New Revenue With Playwire’s Hashed Email API

The biggest problem is that not every site is set up to leverage their collected emails.

Cue Playwire.

Playwire’s hashed email API helps sites drive value using their highly-valuable email list. 

In many cases, publishers already have these emails but haven’t maximized their revenue-driving potential. We help them hash their emails with a simple line of code that protects the privacy of users and allows them to identify their users across multiple sites, allowing them to see CPMs double on known users right away. 

This ties directly into our proprietary data management platform (DMP), segmenting and enriching your audience to drive more ad revenue.

Learn a bit more about how our DMP works in the graphic below.




(Click here to enlarge graphic)

If you thought the value stopped there, think again.

We also work with some of the largest identity providers in the industry, including LiveRamp and The Trade Desk, who are also delving deeper into the world of email hashing. These are the players who track important information about users, thus allowing you to share that information with advertisers up the chain. 

A connection to these identity providers is what allows us to unlock additional spend from advertisers who are already reliant on products such as LiveRamp ID to complete their targeting and identification. And additional spend means increased CPMs and fill rates for you!

The best part: this is just the beginning.

Playwire will continue to add integrations that help our publishers keep up with the widespread adoption of hashed email. Publishers who get on board now will see incremental growth as time passes, without having to do anything additional.

Sounds pretty good, right? Contact us online today to learn more and get started.

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