Hashed Email (HEM)
A hashed email (HEM) is an email address transformed by a one-way cryptographic function into a fixed string that cannot be reversed back to the original address. It lets systems match people on email without exposing the raw address, supporting privacy-safe identity resolution.
Because the same email always produces the same hash, two systems can compare hashes to find matches without sharing the underlying email. This is widely used in audience matching and clean rooms.
Hashing is not the same as anonymization: a hashed email still identifies a person and is treated as personal data, so it must be handled with the same consent and security as raw PII.
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