Question 1

What is a hashed email?

Accepted Answer

A hashed email is the output of running a normalized email address through a one-way function such as SHA-256. Two systems that hash the same address the same way get the same string, so they can match records without exchanging the address itself.

Question 2

Can a hashed email be reversed?

Accepted Answer

Hashing is one-way, but it is pseudonymous rather than anonymous: anyone holding a list of addresses can hash them and look for matches. Treat hashed emails as personal data and share them only with partners you would trust with the plaintext.

Question 3

Should I use SHA-256, SHA-1 or MD5?

Accepted Answer

SHA-256 is the usual default for new integrations and what most ad and identity platforms request. SHA-1 and MD5 are older and still common in existing audience files, so the tool shows all three.

Question 4

Why normalize an email before hashing it?

Accepted Answer

A hash changes completely if one character changes, so "Jane@Example.com" and "jane@example.com" hash differently. Trimming and lowercasing first makes the same person hash the same way everywhere. Data Legion also removes Gmail dots and provider plus tags, because those variants all reach one inbox.

Question 5

Can I enrich a hashed email?

Accepted Answer

Yes. Send a SHA-256, SHA-1 or MD5 hash in the email_hash parameter of the Person Enrichment API and it matches the profile behind it. Use the Data Legion Matching form so the hash lines up with how the profiles are indexed.

Question 6

Is the email I type sent anywhere?

Accepted Answer

No. The hashes are computed by JavaScript in this page. The address is never sent to Data Legion or anyone else, and analytics events record only which hash you copied.

Email Hash Generator

How the two normal forms differ

Common Questions