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Last updated:
July 27, 2026
What HEM and MAID are
A HEM, or hashed email, is an email address that has been scrambled through a one-way function into a string that cannot be reversed back into the original address. It acts as a stable, pseudonymous stand-in for a person across the open web.
A MAID, or mobile advertising ID, is the identifier a phone's operating system assigns for advertising. It is how audiences are recognized and reached inside mobile apps.
What HEM to MAID means
A HEM to MAID connection is simply the association that says a given hashed email and a given mobile ID belong to the same person. With that link in place, an audience built from emails, a CRM list, for example, can be recognized and activated on mobile inventory.
Why this connection matters
Email is the closest thing the open web has to a durable identifier, and mobile is where a large share of activation now happens. HEM to MAID bridges the two.
For any team whose match rates against first-party data have plateaued, adding HEM to MAID connections is one of the highest-impact moves available, because it turns email audiences into reachable mobile audiences without relying on third-party cookies.
How HEM to MAID connections are made
Connections are formed where the evidence supports them, when a hashed email and a device are observed together, for example. Coverage depends on the market and on the email hash type, and there are several common formats, so a strong provider reports coverage by both.
Because people change devices and email habits, these connections are refreshed on a predictable cadence to keep them accurate.
HEM to MAID and privacy
Both sides of the connection are pseudonymous. A hashed email is not a readable address, and a mobile ID is not a name. The connection links two scrambled identifiers, not a personal profile, which is what makes it safe to use at scale.
HEM to MAID in practice
Consider a retail media network with a large logged-in customer base, so it holds many hashed emails, but weak activation in mobile apps where much of its inventory sits. Its email audiences are valuable but hard to reach where it matters.
By adding HEM to MAID connections, the network turns those email audiences into mobile-addressable ones. A shopper known only as an email can now be reached across mobile inventory, and the network's addressable reach climbs without collecting new personal data or relying on third-party cookies. This is an illustrative pattern rather than a specific customer, but it reflects why HEM to MAID is one of the most requested connections.
Frequently asked questions
What is HEM to MAID?
The connection between a hashed email (HEM) and a mobile advertising ID (MAID), which lets an email-based audience be recognized and reached in mobile environments.
What is a hashed email (HEM)?
An email address scrambled through a one-way function into a non-reversible string, used as a stable, pseudonymous stand-in for a person across the open web.
What is a MAID?
A mobile advertising ID, the identifier a phone's operating system assigns for advertising, used to recognize and reach audiences inside mobile apps.
Why does HEM to MAID improve match rates?
It turns email audiences into reachable mobile audiences without third-party cookies, so more of your first-party data becomes addressable where activation actually happens.
Is HEM to MAID privacy-safe?
Both sides are pseudonymous. A hashed email is not readable and a mobile ID is not a name, so the connection links scrambled identifiers rather than a personal profile.
Does HEM to MAID work across countries?
Coverage varies by market and by email hash type, so it is stronger in some countries than others. A good provider reports coverage broken down by country and hash type rather than a single global average.
