Hashed Email

The Short Answer

A hashed email is an email address that has been run through a one-way cryptographic function (commonly SHA-256) so it can be matched against other hashed records without exposing the original, readable email address. Hashed identifiers are widely used for privacy-safe audience matching between platforms, such as uploading a customer list to an ad network without sharing plain-text emails.

How It Works

The plain-text email address is passed through a one-way hashing function, commonly SHA-256, producing a fixed string that cannot be reversed back into the original email. Two systems hashing the same email with the same method produce identical hashes, which is what makes matching possible.

Why It Matters

Hashed identifiers let two platforms match a shared customer without either side ever seeing the other's raw email list, which is why they are the standard for privacy-safe audience matching between an advertiser and an ad network.