What is an Email Hash?

An email hash is a 32, 40, or 64-character code created by running an email address through a hashing algorithm. Whenever you log into a website using your email address, you are recognized throughout your session as a hash. Hashes are used commonly and are a simple standard across the web.

For example, the hash for Bob@liveintent.com looks like this: dc124f8ec1f98e027ebc7655d94b08f4


Hashing an email is a cryptographic security method that transforms an email address into a random code using mathematical techniques. This code (i.e., hash) cannot be reversed, making it a completely anonymous customer identifier. 

All email addresses that you onboard to LiveIntent must be hashed using a hashing function: 

  • MD5 (message-digest algorithm): The output will always be 32 characters. In recent years, MD5 has lost popularity to the SHA family of hashing functions.
  • SHA-1 (secure hash algorithm 1): Designed by the United States National Security Agency as a Federal Information Processing Standard. The output is a hexadecimal number 40 characters long.
  • SHA-2 (secure hash algorithm 2): The successor to SHA-1, the SHA-2 family consists of multiple hash functions with hash values that vary in size, the most common being SHA-256, which produces an output of 64 characters. 


Pro Tip

SHA-256 is considered the most secure option of the three listed above. You can onboard customer audience files in any of the above hash formats to the LiveIntent platform. LiveIntent will generate an encrypted LiveIntent ID to represent the email hashes that you onboard.



Case sensitivity

Hash functions are sensitive to their input.  Two strings, one capitalized and one lower case, will produce two different outputs.  Because of this, it is crucial to stick with lowercasing as a standard for all email address strings.


The email address should also be stripped of any whitespace (leading or trailing spaces) before they are hashed.


Benefits of email hashing

Unlike a third-party cookie, the email address is a stable ID that represents a known customer. It is unique to that individual and remains persistent across all devices, apps, and browsers.

Through hashing, consumer email addresses are transformed into anonymized identifiers that cannot reveal any personally identifiable information, making the email hash the perfect secure people-based identifier.


Hashing your email list

Our recommendation is to use Audience Manager to hash your plain text emails. You can upload a file of the email addresses and Audience Manager will automatically hash them for you. For more information on how to use Audience Manager, visit Overview of Audience Manager.


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